Joint portion processing device and method for enlarging and reproducing image data

ABSTRACT

An image processing apparatus includes a scanner unit for reading an image of an original document, a memory which, if the image is read by the scanner unit in a divided manner as a plurality of partial images, stores the read partial images as respective partial document data, and a joint-portion processing section. The joint-portion processing section is for recognizing joints of the partial document data stored in the memory and for joining the partial document data according to the recognized joints.

This application is a divisional of application Ser. No. 08/132,274,filed on Oct. 6, 1993, U.S. Pat. No. 5,481,375 the entire contents ofwhich are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to image processing apparatuses, such ascopying machines, scanners, facsimiles, and printers, which are capableof enlarging a read image and outputting the image onto a plurality ofsheets of paper in a divided manner. It further relates to imageprocessing apparatuses which are also capable of automatically joiningdivided images together and forming a combined image on one sheet ofpaper other materials.

2. Description of the Prior Art

In order to combine a plurality of images together and to record thecombined image on one sheet of paper, an information recordingapparatus, such as that disclosed in Japanese Examined PatentPublication No. 33752/1981 (Tokukoushou 5-33752), is employed. In thisapparatus, image data for each page is stored as each independent data:for example, image data of 4 pages of A-4 size are combined together,and the reduced image can be copied on one sheet of paper of A-4 size.

However, in the above-mentioned apparatus, since the image data isstored as individual data for each page, and since there is nocorrelation between those individual data, positioning of images is notoperable between pages.

Therefore, in the case of originals, such as a map, that can not be readby one scanning due to its large size or other reasons, in order toconfirm the connections between images carried on the respective pages,it is necessary to reduce each of originals and copy the combined imageon one sheet of paper. Conventionally, in this case, reduced copies aremade page by page; the original of one sheet being formed by trimmingand pasting them; and the original thus formed being again copied.

However, such images copied in the divided manner as described above arequite likely to have problems, such as lines that appear on the edges,overlapped images, loss of images, etc. Therefore, trimming theseimages, positioning them, etc. are troublesome and time consuming tasks.Moreover, in the above method, when reduced copies are made for therespective pages, it is difficult to determine the setting of areduction rate while taking into consideration a finished state of thecopy. Further, since slight errors are inevitable in the reduction ratesfor the respective pages, offsets might be produced at the joints due tothe trimming and pasting tasks.

Further, in the case of joining torn pieces of an original, theconventional method is that the original of one sheet is formed bypasting the torn pieces together while paying attention to the shapes ofthe torn pieces and the joining portions of the images, and that theoriginal thus joined together is again copied.

However, in such a case as to form the original of one sheet by pastingthe torn pieces together, the pasting process, which has to be carriedout while paying attention to the shapes of the torn pieces and thejoining portions of the images, is troublesome and time consuming,thereby reducing the efficiency of the work. Moreover, since offsets arequite likely to appear at the joints, an image, which is obtained bycopying the original thus pasted together, tends to have shadows atportions corresponding to the joints. This greatly reduces theresolution of the image.

Furthermore, in the case of obtaining an enlarged image by enlarging asmall document such as a map, etc. by the use of, for example, a copyingmachine as an image processing apparatus provided with an enlargingfunction, if the image of the document is enlarged to a size that cannot be covered by maximum-sized copy sheets available in the copyingmachine, the conventional method is that portions of the document imageare copied onto a plurality of copy sheets in a divided manner at adesired rate of magnification, and then the resulting copied sheets arepasted together.

In this method, since it is difficult to tell the copiable region whenthe portions of the document image are copied onto a plurality of copysheets, it is not easy to determine how to divide the document image.Further, troublesome tasks are required in removing the excessiveoverlapped portions when the resulting copied images are pastedtogether.

In order to improve the operability of the above method, there has beenproposed another apparatus wherein, in the case when a document iscopied in a predetermined rate of magnification, if the resulting copiedimage seems to become larger than copy sheets of the specified size, thedocument image is automatically divided into a plurality of images, andthe divided document images are copied on individual copy sheets.

However, even in the above conventional apparatus, although iteliminates the need for conducting the copying operation while takingaccount of the dividing method of the document image, it merely dividesthe document image in a predetermined manner and delivers them onindividual copy sheets. Troublesome and time consuming tasks arerequired in removing the excessive overlapped portions when theresulting copied images are pasted together and in positioning thedivided documents. Additionally, there has been proposed still anotherapparatus, wherein upon copying a document image, the image position inrelation to copy sheets is automatically shifted to form a margin havinga specified width, that is, a binding margin. However, this apparatusalso fails to solve the above problems.

SUMMARY OF THE INVENTION

It is an objective of the present invention to provide an imageprocessing apparatus which is capable of joining a plurality ofdocuments together without causing any adverse effects on the efficiencyof work as well as automatically conducting a variable magnificationoperation on the combined image in accordance with the size of copysheets.

It is another objective of the present invention to provide an imageprocessing apparatus which is capable of joining together a plurality oftorn pieces of an image accurately and efficiently without causing anyoffsets and shadows in the image at portions corresponding to thejoints.

It is still another objective of the present invention to provide animage processing apparatus which is capable of improving the efficiencyof work that is required for obtaining one image by pasting togetherimages that have been released on a plurality of copy sheets in adivided manner.

In order to achieve the above objectives, the image processing apparatusof the present invention comprises: an input means for reading an imageof a document; a storage means for storing a plurality of images thathave been read by the input means as partial document data; and ajoint-portion processing means for recognizing joints of the partialdocument data that have been stored in the storage means and for joiningthe respective partial document data.

With the above arrangement, in the case of using a document that has tobe read by the input means in a divided manner due to, for example, itslarge size or other reasons, and forming a reduced image of the originalimage on a recording medium of a desired size by reducing the image ofthe document, the images that have been read in the divided manner arestored in the storage means as the respective document data. Thedocument data stored in the storage means are then respectivelysubjected to a joint-recognizing operation and a positioning operationin the joint-portion processing means.

Therefore, in the case of forming a reduced image by joining togetherimages that have been read in a divided manner and conducting a variablemagnification operation on the image to a desired size, the presentinvention eliminates troublesome and time consuming tasks such asreducing divided portions of a document respectively, and trimming andsticking together the reduced portions to form one document, as well aseliminating the necessity of time consuming calculations on reductionrate, etc. Thus, it becomes possible to improve the efficiency of work,and to prevent offsets that would occur at the joints of the combineddocument. This ensures high quality in the images.

Moreover, in the case where the partial documents contain a lot ofoverlapped portions, if the partial documents are joined together afterthey have been respectively reduced, the joined image is prone to havemargin portions. However, by the use of the arrangement of the presentinvention wherein the reducing operation is performed after havingcombined the partial document data together, it is possible to eliminatethe negative effect on picture quality.

In the above-mentioned joint-portion processing means, the followingmeans are provided to further improve the quality in the images.

That is, the joint-portion processing means is provided with a shiftingmeans for shifting the respective document data, in the parallel ororthogonal direction with respect to a joint, so as to make therespective data consistent with each other. It is alternatively providedwith a rotative movement means for rotating one of the document datacentered on a predetermined position such as its corner or other pointsso as to make the respective data consistent with each other. Therefore,even in a case where a corner of the divided document is not read orwhere the document data are read in a tilted manner, it is possible toreduce offsets that would occur at the joints of the combined documentdata.

Moreover, the joint-portion processing means is arranged to discriminatedata-loss areas of the image in accordance with the positionalrelationship of the document data, to create compensating data based onimages located at the ends of the document data that are to be joined,and to compensate for the data-loss area. Therefore, even in the casewhere, upon reading an image by the use of the input means, a portion ofthe image is not read, compensating data are created based on imageslocated around the data-loss area so as to compensate for the data-lossarea. This makes it possible to enhance the picture quality byeliminating shrinkage of images and unnatural appearances that wouldoccur at the joints.

Moreover, in the case where the edge of a document is read as a line,the joint-portion processing means erases the line by discriminating itfrom the other images of the document. Therefore, it is possible toavoid the disadvantage of having extra lines at the joints of the image,thereby eliminating unnatural appearances at the joints.

Furthermore, the joint-portion processing means recognizes that an area,from a position determined as a joint in one of the document data to anend of the other of the document data situated on the former documentdata, is an overlapped portion of the image, and conducts a positioningoperation after erasing the overlapped portion. Therefore, even in acase where upon reading, an overlapped portion is formed due to offsetsof the image, the joint-portion processing means erases the overlappedportion by discriminating it from the other images of the document,thereby eliminating unnatural appearances at the joints.

The joint-portion processing means is also provided with an adjustingmeans for adjusting the density data so as to minimize differencesbetween the density data of the document data upon conducting a joiningoperation. Therefore, it is possible to reduce changes in density thatwould occur at the joints when the respective document data are joinedtogether, thereby reducing unnatural appearances at the joints.

Moreover, in the joint-portion processing means, sides having thedocument data, on which a joining operation is conducted with respect tothe document data, are specified by the sequence of inputting the imagesand an instruction for changing into a new line that is given byinserting a predetermined document to be read. These specified sidesgive a basis on which the data are retrieved. The joints are recognizedand positioning is conducted. Therefore, it becomes possible to performthe joining operation quickly and accurately without requiring excessivetime for retrieving data or other processes even if complicated imagesare used, or even if a number of documents are read in the joiningoperation.

Furthermore, in the case of using torn and separated pieces of adocument, the joint-portion processing means recognizes the shapes ofthe torn pieces of the document from the document data stored in thestorage means, positions the document data so as to allow the tornpieces to be joined together, and erases data corresponding to shadowsthat would appear on the joints. Therefore, this makes it possible toimprove the efficiency of work in joining the torn pieces of thedocument together. Further, since it is possible to prevent offsets andshadows that occur at the joints, the high quality in the image can beachieved.

Moreover, when a plurality of torn pieces of a document, which arearranged in the scanning direction .of the input means, are successivelyscanned by the input means, these images of the torn pieces of theoriginal are stored in the storage means as document data. Then, amongthe document data, by comparing the document data corresponding to therear portion of a preceding document piece read earlier by the inputmeans with the document data corresponding to the leading portion of thesucceeding document piece read in the following scanning, thejoint-portion processing means recognizes the shapes of the rear portionand the leading portion of the torn document pieces. Successively,positioning is made on the document data so that the torn documentpieces are joined to each other based on the shapes of the rear portionand the leading portion, and data corresponding to shadows that wouldappear at the joints are erased.

Therefore, by arranging the torn pieces of a document in the scanningdirection of the input means so that the torn edges to be joined arealigned face to face with each other, the process for finding out thetorn edges to be joined can be simplified upon conducting thepositioning of the document data so as to connect the torn pieces. Thismakes it possible to simplify the joining operation and to shorten thetime of the operation.

When a plurality of torn pieces of a document are arranged with theircorresponding torn edges placed face to face in accordance with theapproximate original positional relationship before it was torn, theimages of these torn pieces of the document are read by the input meansand stored in the storage means as a series of document data. Then, inthe joint-portion processing means, data of a shadow, which are locatedbetween the document data that seem to be consistent and which appear atthe joint between the torn edges, are detected, and data located at bothsides of the data of the shadow are recognized as the document data ofthe torn edges of the torn pieces. Further, the joint-portion processingmeans recognizes the shapes of the torn edges from the document data ofthese torn edges. Successively, positioning is made on the document dataso that the torn document pieces are joined to each other, and the datacorresponding to shadows that would appear at the joints are erased.

Therefore, by arranging a plurality of torn pieces of a document withtheir corresponding torn edges placed face to face in accordance withthe approximate original positional relationship before it was torn, theprocess for finding out the torn edges to be joined can be simplifiedupon conducting the positioning of the document data so as to connectthe torn pieces. This makes it possible to simplify the joiningoperation and to shorten the time of the operation.

Moreover, for example, in the case of reading images carried on twoopened pages of a book or the like having a considerable thickness bythe use of the input means, any shadows that appear in the document dataare erased in the joint-portion processing means. Moreover, the documentdata, after having been subjected to the shadow-erasing operation, areretrieved for portions having coincident image information, and subjectto a positioning operation. Then, the document data are compensated forany loss of data that is caused by the shadow-erasing operation, and thedocument data combined by the joining operation are subject to avariable magnification operation by the variable magnification means inaccordance with the size of the recording medium whereon the combinedimage is formed.

Therefore, even if any shadows appear in the document data stored in thestorage means due to the thickness of the book, the shadow-erasingoperation and the compensating operation for the loss of data areexecuted on the document data, and the document data are joined togetheraccurately.

Moreover, marks are put on the document data to determine approximatepositions at which the joining operation is conducted in the images ofthe document data stored in the storage means. The joint-portionprocessing means then retrieves the document data for portions havingcoincident image information in accordance with the marks. The marks aregiven in the form of, for example, a line drawn in the proximity of aborder between a necessary portion and an unnecessary portion on theimage. Lines and marks indicating positions of features that are locatedin the positions at which the joining operation is conducted, and thepositioning of the document data is then conducted.

Therefore, the above arrangement makes it possible to providehigh-quality images without offsets or other problems caused at thejoints. Further, in the case of conducting the joining operation ondocuments that have, for example, a space portion around the image orthe same images that are formed on the edges of the two consecutivepages in an overlapped manner, if a retrieving process is conducted fromthe end of the image in order to detect portions having coincident imageinformation, the storage capacity is used in a wasteful manner, theprocessing time is excessively prolonged, and the possibility of errorsincreases. However, by conducting the retrieving operation in accordancewith the above-mentioned marks, it is possible to save the storagecapacity and to shorten the retrieving time, etc., thereby ensuringaccurate, quick operations.

Moreover, in order to achieve the aforementioned objectives, the imageprocessing apparatus of the present invention is provided with an inputmeans for reading an image of a document; a storage means for storingimages that have been read by the input means as document data; adivision-enlargement processing means for dividing and enlarging theimage data stored in the storage means such that the divided image dataare respectively made into independent image data; and a margin-portioncreating section for adding to the image data that have been divided bythe division-enlargement processing means additional image data forcreating a pasting margin along one of the joint portions between thedivided image data.

With the above arrangement, the image of a document that have been readby the input means are stored in the storage means as image data. In thedivision-enlargement processing means, the image data are divided, andalso enlarged at a predetermined rate of magnification such that thedivided image data are respectively made into independent image data.Then, in the margin-portion creating section, additional image data areadded to the image data that have been divided by thedivision-enlargement processing means additional in order to create apasting margin along one of the joint portions between the divided imagedata. The additional image data form, for example, colored pastingmargins when seen after printed. Therefore, on the divided images of thedocument that are released from the image processing apparatus of thepresent invention, and formed on the individual copy sheets, there areclearly formed pasting margins along the joint portions of the dividedimages that are to be joined. This arrangement makes it possible toimprove the efficiency of work in the case of pasting the divided imagestogether to form one complete enlarged image of the original image.

For a fuller understanding of the nature and advantages of theinvention, reference should be made to the ensuing detailed descriptiontaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a construction of an image processingsystem that is installed in a digital copying machine of the presentinvention.

FIG. 2 is an explanatory drawing that schematically shows theconstruction of the digital copying machine of FIG. 1.

FIG. 3 is a flow chart showing the sequence of processes that arecarried out during a joining operation of document data in the digitalcopying machine of FIG. 1.

FIG. 4(a) is an explanatory drawing that indicates retrieving areas ofdocument data.

FIG. 4(b) is an explanatory drawing that shows a positioning operationof the document data.

FIG. 4(c) is an explanatory drawing that shows a resulting imageobtained after the document data shown in FIG. 4(a) have been subject toa combining operation and a variable magnification operation.

FIGS. 5(a) and 5(b) respectively show plan views of torn pieces of adocument.

FIG. 5(c) is an explanatory drawing that shows document data stored inan image memory.

FIG. 5(d) is an explanatory drawing that shows a resulting image afterthe joining operation.

FIG. 6 is a flow chart showing the sequence of processes that arecarried out during a joining operation of the document data.

FIG. 7 is a flow chart showing the sequence of processes that arecarried out during a feature extraction of documents in the joiningoperation.

FIG. 8 is an explanatory drawing that shows the positions of documentdata in the image memory.

FIG. 9 is an explanatory drawing that shows retrieving areas of thedocument data stored in the image memory.

FIG. 10 is a flow chart showing the sequence of processes that arecarried out during a decision on coincidence or non-coincidence of thedocument data in the joining operation.

FIG. 11 is a flow chart showing the sequence of processes that arecarried out during a judgement as to the completion of all the dataprocessing in the joining operation.

FIG. 12 is an explanatory drawing that shows the positions of images inthe case of executing the joining operations on four images.

FIG. 13(a) is a plan view showing torn pieces of a document.

FIG. 13(b) is an explanatory drawing that show the positions of the tornpieces of the document on the document platen and scanning direction ofthe document.

FIG. 14 is a flow chart showing the sequence of processes that arecarried out during a compensation for loss of data in the joiningoperation.

FIG. 15 is an explanatory drawing that shows document data in questionfor the compensation for loss of data.

FIG. 16 is a flow chart showing the sequence of processes that arecarried out during a compensation for loss of data in the joiningoperation.

FIG. 17 is a flow chart showing the sequence of processes that arecarried out during a judgement as to the completion of all the dataprocessing in the joining operation.

FIG. 18 is an explanatory drawing that shows joining lines drawn ondocuments to be joined together.

FIG. 19 is an explanatory drawing that shows feature-indicating linesdrawn on documents to be joined together.

FIG. 20 is an explanatory drawing that shows enclosing marks drawn ondocuments to be joined together.

FIG. 21 is an explanatory drawing that shows document data that werepositioned by the joining operation.

FIG. 22 is an explanatory drawing that shows a copy obtained by thejoining operation.

FIG. 23(a) is a plan view showing torn pieces of a document.

FIG. 23(b) is an explanatory drawing that shows the positions of thetorn pieces of the document on the document platen and scanningdirection of the document.

FIG. 23(c) is an explanatory drawing that shows an image released fromthe digital copying machine after the joining operation.

FIG. 24 is a flow chart showing the sequence of processes that arecarried out during a feature-extraction of the torn pieces of thedocument in the joining operation.

FIG. 25 is an explanatory drawing that shows a document on which thejoining operation is conducted.

FIGS. 26(a) through 26(g) are explanatory drawings that respectivelyshow an input sequence for images that specifies the positionalrelationship between document data in the joining operation.

FIG. 27(a) is an explanatory drawing that shows document data having aloss of data for which a compensating operation is conducted.

FIG. 27(b) is an explanatory drawing that shows a distance and an offsetbetween document data.

FIG. 27(c) is an explanatory drawing that shows document data afterhaving been subject to the compensating for loss of data.

FIG. 28 is an explanatory drawing that shows a line caused by the edgeof a document in the document data stored in the image memory.

FIG. 29 is a plan view indicating a document platen that is installed inthe digital copying machine.

FIG. 30(a) is a sectional view taken along the line A--A of the documentplaten of FIG. 29.

FIG. 30(b) is an explanatory drawing that shows black and white levelsthat are detected depending on the position of the document shown inFIG. 30(a).

FIG. 30(c) is an explanatory drawing that shows black and white levelsafter the edge of the document has been erased.

FIG. 31 is an explanatory drawing that shows a case where an overlappedportion appears in the document data stored in the image memory.

FIG. 32 is an explanatory drawing that shows a state where theoverlapped portion of the document data has been compensated for.

FIG. 33 is an explanatory drawing that shows a copy obtained by thejoining operation.

FIG. 34 is an explanatory drawing that shows a void area and an imageloss that appear on a copy sheet after copying.

FIG. 35 is an explanatory drawing that shows retrieving areas for imagedata at joints in the document data.

FIG. 36 is a flow chart showing the sequence of processes that arecarried out when compensating for the loss of the images at the joints.

FIG. 37(a) and FIG. 37(b) are explanatory drawings that show a joiningoperation of images when there is one joint.

FIGS. 38(a) through 38(d) are explanatory drawings that show a joiningoperation of images when there are two or more joints.

FIG. 39 is a block diagram showing a construction of an image processingdevice that is installed in a digital copying machine of the presentinvention.

FIG. 40 is a flow chart showing a sequence of processes that are carriedout when a compensating operation for densities of images is conducted.

FIG. 41(a), FIG. 41(b) and FIG. 41(c) are explanatory drawings that showa joining operation of images at respective joints.

FIG. 42 is a block diagram showing a construction of an image processingsystem that is installed in a digital copying machine of the presentinvention.

FIG. 43(a) is a perspective view of a book of maps that is used as adocument in a joining operation by the use of the image processingsystem of FIG. 42.

FIGS. 43(b) and 43(c) are explanatory drawings that show a state of theimage memory wherein document data are stored from the book of mapsshown in FIG. 43(a).

FIG. 44 is a flow chart showing a sequence of processes that are carriedout during a joining operation.

FIG. 45 is an explanatory drawing that shows setting of coordinates onthe image memory.

FIGS. 46(a) and 46(b) are explanatory drawings that show densitydistributions at image ends of the document data.

FIG. 47 is a flow chart showing the sequence of processes that arecarried out during a shadow-erasing operation for the document data.

FIG. 48 is a flow chart showing the sequence of processes that arecarried out when the amount of positioning is set so as to conduct thejoining operation.

FIG. 49 is a flow chart showing the sequence of processes that arecarried out when compensating for the loss of data that occurred by thejoining operation.

FIG. 50 is an explanatory drawing that shows a state of image that isobtained after the compensating operation for the loss of data.

FIG. 51 is a block diagram showing a construction of an image processingsection that is installed in the digital copying machine.

FIG. 52 is a flow chart showing a sequence of processes that are carriedout in a division-enlargement processing section of the digital copyingmachine.

FIG. 53 is an explanatory drawing that shows the processing operationsof a UCR.BP processing section shown in FIG. 3.

FIG. 54(a) is a front view showing an original that is to be divided andenlarged by the copying machine; and

FIG. 54(b) is an explanatory drawing that shows individual image dataafter the image of the original is divided and enlarged.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1 through 5, the following description will discussone embodiment of the present invention.

As illustrated in FIG. 2, a digital copying machine, which is installedin an image processing apparatus in accordance with the presentembodiment, is provided with a document platen 27 made of a hard glassplate, etc. that is installed on the upper surface of a copying machinemain body 26. Below the document platen 27 is disposed a scanner unit(input means) 22. The scanner unit 22 is constituted of: a lamp unit 1;mirrors 2, 3 and 4; a lens unit 5; and a CCD (Charge Coupled Device)sensor 6. A reflected light beam, which is obtained by irradiating adocument (not shown) placed on the document platen 27 by the lamp unit1, is directed to the light-receiving face of the CCD sensor 6 throughthe mirrors 2, 3 and 4 and the lens unit 5, and detected therein aselectric signals.

A laser driver unit 7 is installed below the scanner unit 22. Image dataof the document, which are detected by the CCD sensor 6 as the electricsignals, are temporarily stored in an image memory (storage means) 43installed in the image processing apparatus shown in FIG. 1, which willbe described later. After having been subject to predeterminedprocessing in the image processing apparatus, the image data are sent tothe laser driver unit 7. The laser driver unit 7 has a semiconductorlaser for projecting a laser beam in response to image data inputtedthereto, a polygon mirror for diffracting the laser beam in a constantangular velocity, an f-θ lens for correcting the laser beam that hasbeen diffracted in the constant angular velocity so that it is againdiffracted in a constant angular velocity on a photoreceptor drum 10,and other devices.

A laser beam released from the laser driver unit 7 is reflected by themirrors 8 and 9 that are disposed in the light path, and projected ontothe photoreceptor drum 10, which is capable of rotating in the directionof arrow A as shown in FIG. 2, thereby forming an electrostatic latentimage on the photoreceptor drum 10.

On the periphery of the photoreceptor drum 10, are disposed a charger 16for charging the photoreceptor drum 10 so as to impart a predeterminedvoltage to its surface prior to an exposure executed by laser driverunit 7. Further, from the charger 16 along the rotation direction of thephotoreceptor drum 10, are installed in the following order: adeveloping device 28 for forming a toner image by supplying toner to theelectrostatic latent image on the photoreceptor drum 10; a transferringbelt 17 whereto the toner image on the photoreceptor drum 10 istemporarily transferred; a cleaning device 21 for removing residualtoner from the photoreceptor drum 10; an electrostatic eliminating lamp15 for eliminating residual static electricity from the photoreceptordrum 10 prior to the next charging operation, etc.

The developing device 28 includes a black developer vessel 11, a yellowdeveloper vessel 12, a magenta developer vessel 13, and cyan developervessel 14, and those developer vessels 11 through 14 respectively housetoners having corresponding colors. The transferring belt 17, which isprovided in the form of an endless belt, is installed so as to move inthe direction of arrow B in the drawing, and one portion of thetransferring belt 17 is pressed against the photoreceptor drum 10 suchthat the toner image on the photoreceptor drum 10 is transferredthereonto.

On the paper-feeding side with respect to the transferring belt 17, areinstalled a resist roller 19 for supplying copy sheets to thetransferring belt 17 at predetermined intervals, a feeding cassette 20for housing copy sheets, and a feeding tray 23 on which copy sheets areplaced. Further, a feeding roller 24 for transporting copy sheets, atransporting roller 25, etc. are installed in the proximity of thefeeding cassette 20 and the feeding tray 23. Below the transferring belt17, is installed a transferring roller 18 which presses a copy sheetsent thereto from the resist roller 19 against the transferring belt 17,and allows the toner image on the transferring belt 17 to be transferredonto the copy sheet.

On the paper-discharging side with respect to the transferring belt 17,are installed a conveyer belt 30 for conveying the copy sheet bearingthe toner image, a fixing device 31 for fusing the toner image onto thecopy sheet by heat, a discharge roller 32 for discharging the sheet ofcopy paper after the fusing operation out of the apparatus.

In the above arrangement, a color-copy (3 color copy) operation iscarried out in the following sequence. First, the charger 16 uniformlycharges the surface of the photoreceptor drum 10, and the scanner unit22 executes the first scanning. The image data (R.G.B) detected by theCCD sensor 6 are processed in the image processing section, and arereleased from the laser driver unit 7 as a laser beam representative ofyellow data. The surface of the photoreceptor drum 10 is exposed by thelaser beam, and an electrostatic latent image for yellow-use is formedon the exposed portion of the photoreceptor drum 10. Then, yellow toneris supplied to the electrostatic latent image within the image regionfrom the yellow developer vessel 12, and a yellow toner image is thusformed.

Next, the yellow toner image is transferred onto the transferring belt17 that is pressed against the photoreceptor drum 10. At this time,although some toner that has not been consumed in the transferringprocess remains on the surface of the photoreceptor drum 10, theresidual toner is scraped off by the cleaning device 21. Moreover, theelectrostatic eliminating lamp 15 eliminates the residual charge on thesurface of the photoreceptor drum 10.

After completion of the above processes, the charger 16 again chargesthe surface of the photoreceptor drum 10 uniformly, and the scanner unit22 executes the second scanning. The image data are processed in theimage processing section, and are released as a laser beamrepresentative of magenta data. The surface of the photoreceptor drum 10is exposed by the laser beam, and an electrostatic latent image formagenta-use is formed on the exposed portion of the photoreceptor drum10. Then, magenta toner is supplied to the electrostatic latent image,and a magenta toner image is thus formed. Thereafter, this toner imageis transferred onto the transferring belt 17 so as to be superimposed onthe former yellow toner image. After the cleaning device 21 and theelectrostatic eliminating lamp 15 have carried out the same processes asdescribed earlier, the charger 16 again charges the surface of thephotoreceptor drum 10 uniformly, and the scanner unit 22 executes thethird scanning. An electrostatic latent image for cyan-use is formed byexposing the photoreceptor drum 10 with a laser beam representative ofcyan data. Then, cyan toner is supplied to the electrostatic latentimage from the cyan developer vessel 14, and a cyan toner image is thusformed. Thereafter, this cyan toner image is transferred onto thetransferring belt 17 so as to be finally superimposed on the formertoner images.

A complete toner image on the transferring belt 17, which has beenformed by superimposing three toner images, is transferred onto a copysheet, and the complete toner image is fused onto the copy sheet byheat, and then the copy sheet is discharged out of the apparatus by thedischarge roller 32.

The sequence of processes described above is a sequence for carrying outa three-color copying operation. In the case of a four-color copyingoperation, a process using black toner in the black developer vessel 11is added to the above-mentioned sequence. In the case of a mono-colorcopying operation, black toner is supplied to the electrostatic latentimage from the black developer vessel 11, and the black toner image thusformed is transferred onto a copy sheet through the transferring belt17.

Referring to FIG. 1, the following description will discuss theconstruction, functions, etc. of the image processing section forsuitably processing the image data read by the CCD sensor 6 and forreleasing the data to laser driver unit 7.

As shown in FIG. 1, the image processing section, which executes colorreproduction according to documents and joint-portion processing onimages read from divided or broken documents, is constituted of a RGBlevel-adjusting section 40, an A/D convertor 41, a shading correctionsection 42, an image memory 43, a joint-portion processing section(joint-portion processing means) 48, a τ correction section 49, ablack-document detection section 50, a masking section 51, a UCR(UnderColor Removal)-BP(Black Print) processing section 52, a sharpness filter53, a variable magnification section (variable magnification means) 54,a density processing section 55, a color-balance adjusting section 56,tone processing section 57, etc.

In the image processing section, analog signals, that is, document dataof R, G, B obtained from the CCD sensors 6, are compensated for theirdispersions between R, G, B due to the respective CCD sensors, and arethen converted into digital signals in the A/D convertor 41. Thereafter,the document data are subject to a shading correction for correctingvariations in sensitivity of the CCD sensor for each picture element,unevenness in brightness of the lens, etc. in the shading correctionsection 42, and are temporarily stored in the image memory 43.

In this case, if a joining mode, which will be described later, isspecified, a plurality of documents that are to be joined for theirimages are successively scanned, and those images are separately storedin the image memory 43 as respective document data. The document dataare sent from the image memory 43 to the joint-portion processingsection 48.

The joint-portion processing section 48 includes a joint recognitionsection 44, a data-arranging section 45, a positioning section (shiftingmeans) 46, and a combination processing section 47. The document datainputted to the joint-portion processing section 48 are first sent tothe joint recognition section 44 where the joints of the documents arerecognized, and are then sent to the data-arranging section 45 where thecorresponding joints are arranged face to face with each other.Successively, the subsequent data are sent to the positioning section 46where positioning is made so that images located at joints have aconsistency, and are then sent to the combination processing section 47where they are combined together. After completion of the processing inthe joint-portion processing section 48, the data of the documents areagain inputted to the image memory 43. Here, as to the sequence of theoperations in the above joint-portion processing, its detailedexplanation will be given later.

Together with data released from the black-document detection section 50for making a discrimination between mono-color copy and color copy, thedata of the documents released from the image memory 43 are inputted tothe τ-correction section 49 where a τ-correction is executed so as toadjust contrast and brightness.

The τ-correction is carried out so that the output signal from the CCDsensor and the output density of a printer or the like are corrected intone to have a linear relationship. In other words, if the RGB dataobtained from the CCD sensor are released to the printer or the likewithout being subject to the correction, the dark portions of thedocument are reproduced as by far darker portions due to the fact thatthe dot diameter of the printer is normally greater than that of thetheoretical value. Therefore, it is necessary to make a compensation forthe data so that dark portions become brighter. This correction is theτ-correction, which is also referred to as "tone correction".

In the masking section 51, the data of R, G, B, which have been subjectto the τ-correction, are converted into data of C, M, Y (Cyan, Magenta,Yellow) by executing suitable calculations. In the UCR-BP processingsection 52, the C, M, Y data of the document are subject to the UCRprocessing for removing grey components from toners of three colors, C,M, Y, and for replacing them with black toner, as well as subject to theBP processing for adding black toner to the toners of three colors.Thus, B_(K) (black) data are added to the C, M, Y data of the document.

The UCR (Under Color Removal) is a method by which superimposed portionsof C, M, Y, that is, black-colored portions, are replaced with blacktoner so that the toners of respective colors C, M, Y are reduced intheir amounts of use. In general, the rate of replacement by black toneris 30-40 percent at present. The following advantages are obtainedthrough the above processing: It becomes easier to adjust "GrayBalance". The reproducible range of shadow portions is expanded. Blackportions are preferably reproduced. It becomes possible to reduce thetotal amount of toner.

The sharpness filter 53 emphasizes the sharpness of the C.M.Y.B_(K) dataof the document. Further, the variable magnification section 54 and thedensity processing section 55 execute suitable processing on thesubsequent data so as to impart a specified size and density to theimage. The color-balance adjusting section 56 and the tone processingsection 57 respectively execute the balance adjustments and toneprocessing on the respective colors, and the subsequent data areinputted to the laser driver unit 7. Thereafter, an electrostatic latentimage is formed on the photoreceptor drum 10 by the laser beam releasedfrom the laser driver unit 7, and the aforementioned processes aresuccessively carried out, thereby producing a copied image on a copysheet.

Referring to the flow chart of FIG. 3, an explanation will be given ofthe sequence of the operations that are carried out in the joint-portionprocessing of the data of a plurality of documents.

Firstly, a joining mode is selected through an operation panel, notshown, (S1), and when a plurality of documents are scanned (S2), dataread through the scanner unit 22 provided with the CCD sensors 6 arestored in the image memory 43 (S3).

Successively, joints in the respective images of read data of thedocuments are detected (S4). In other words, image informationcorresponding to predetermined lines of data from the surrounding edgeof each document or from the end of each image is retrieved so as torecognize peculiar lines and characters, and comparison is made betweenrespective portions of document data according to the recognizedpeculiar lines and characters in order to find similar portions to forma joint. Then, at S5, a judgement is made as to whether or not jointsare present, thereby discriminating the presence or absence of detectionof joints. If there is no detection of joints, that is, if nocoincidence is found in the features and shapes in any portions betweenthe respective document data, a warning display indicating "NO" is givento inform that no joining process is operable (S6), thereby stopping theoperation.

In contrast, if there is a detection of a joint at S5, the judgement ismade as "YES", and the data of documents are arranged in thedata-arranging section 45 so that corresponding sides having image datato form a joint are aligned face to face with each other (S7). Next,positioning is carried out in the positioning section such that thebest-suited position of the image data is found by checking theconsistency of the data while shifting the data of one document in themain scanning direction or in the sub scanning direction, with the imagedata of the other document maintained in a fixed state (S8). Thereafter,in the combination-processing section 47, the data of the documents arecombined together (S9), and subject to a shadow-erasing operation, thusforming data of one complete document. This operation is carried out inthe combination-processing section.

Next, at S10, a judgement is made as to whether or not the size of copysheets for use in printing the document data is specified. If the sizeof the copy sheets is not specified, the judgement is made "NO", therebyselecting copy sheets having the largest size among the copy sheets thatare set in the digital copying machine (S11), and a variablemagnification operation is carried out to form reduced document data inaccordance with the copy sheets having the largest size (S12). Incontrast, if the size of the copy sheets is specified, the judgement ismade as "YES" at S10, and a variable magnification operation is carriedout in accordance with the size of copy sheets that has been specified(S12). After completion of the variable magnification operation,conversion of the coordinates is executed on the document data accordingto the longitudinal feeding or the lateral feeding of the copy sheets,if necessary, and the subsequent data are released to the laser driverunit 7, thereby carrying out copying operations of the combined image oncopy sheets (S13). The steps, S10 and S11, are carried out in thecombination-processing section 47, and the step S12 is carried out inthe variable magnification section 54.

Explanations of the above processing are given in detail hereinbelow byexemplifying two cases wherein a map carried on consecutive two pagesare joined together and a plurality of torn pieces of a document arejoined together. In the case when two pages of image data 58 and 59 of amap are respectively stored in the image memory 43, as is shown in FIG.4(a), image information corresponding to predetermined lines of datafrom the end of each image of the document data 58, 59 (indicated byregions having slanting lines) is retrieved so as to recognize peculiarlines and characters. Then, comparison is made between respective pagesof the document data 58 and 59 according to the recognized peculiarlines and characters so as to find similar portions to form a joint.

Then, as illustrated in FIG. 4(b), the pages of the document data 58 and59 are arranged so that corresponding sides having image data to form ajoint are aligned face to face with each other, and with one of thepages of the document data 58 maintained in a fixed state, thebest-suited position of the image data where the portions of the imageare suitably joined together is found by checking the consistency of thedata while shifting the other page of the document data 59 in the mainscanning direction or in the sub scanning direction, as is indicated byalternate long and two short dashes lines in FIG. 4(b). Thus, the imageson the pages are combined together to form document data to be copied onone sheet. Thereafter, a variable magnification operation is carried outin accordance with the size of copy sheets for use in copying, andconversion of the coordinates is executed, if necessary, therebyproducing a reduced copy 60 as shown in FIG. 4(c).

Further, for example, as is shown in FIGS. 5(a) and 5(b), in the casewhen two images of torn pieces 61 and 62 of a document are respectivelyread by the scanner unit 22, document data 61 and 62 are stored in theimage memory 43 as shown in FIG. 5(c). When a joining operation isconducted on the document data 61 and 62, data corresponding topredetermined lines from the periphery of each image (indicated byregions having slanting lines) are first retrieved so as to extractpeculiar lines and characters, and their shapes are recognized. Then,while searching for coincidence of the shapes, portions at which theextracted features become coincident with each other are detected.

When a joint is detected, the document data are arranged so thatcorresponding sides having image data to form the joint are aligned faceto face with each other, and positioning is made so that the featuresand shapes become coincident with each other. Thereafter, the documentdata are combined together, and at this time data corresponding to ashadow that appears at the joint are erased, and a compensatingoperation for the loss of data caused by the erasing operation iscarried out so as not to result in any unnatural appearance. Afterhaving been combined together, the subsequent document data are subjectto a variable magnification operation in accordance with the specifiedsize of copy sheets and a conversion on the coordinates, if necessary,and are released to the laser driver unit 7. These operations result ina reduced copy 63 as shown in FIG. 5(d).

Further, the digital copying machine of the present embodiment isprovided with a function by which, if a plurality of combinations arefound in the positioning of the document data that has been conducted bycomparing the extracted features and shapes of the images, eachcombination may be combined and reduced so as to make a sample copy onone sheet. With such a function, the operator can select a desiredcombination from the samples of the combinations. This results in a moreaccurate joining operation.

As described above, in the digital copying machine of the presentembodiment, when consecutive images carried on a plurality of pages,such as images of a map, are combined together to form a copy on onesheet, those pages are respectively read by the scanner unit 22, andstored in the image memory 43. Joints of the respective pages aredetected, and automatically joined together. The processed data aresubject to a variable magnification so as to have a specified size, andare used to form a complete copied image. Therefore, different from theaforementioned conventional method, which has required time consumingcalculations on reduction rate, etc. and troublesome tasks, such as,trimming and sticking together reduced pages, the present embodimentmakes it possible to improve the efficiency of work, and to preventoccurrences of offsets at the joints of the combined document. Since itis no longer necessary to repeatedly make copies, wasteful use of toner,copy sheets, etc. can be prevented.

Further, as described above, in the digital copying machine of thepresent embodiment, images on torn pieces of a document are read by thescanner unit 22 for each piece, and stored in the image memory 43 asrespective document data. The positioning of the document data iscarried out by recognizing the joints and shapes of the document datathus stored. Therefore, troublesome tasks, such as finding thecoincident portions of the images and shapes between the torn pieces andpasting them together skillfully, are no longer needed, and the tornpieces of the document are automatically combined accurately to producea completely combined image; this results in an improvement in theefficiency of operation. Further, since the digital copying machine ofthe present embodiment also has a function by which shadows, which occurat portions corresponding to joints, are erased, it is possible toensure high-quality in the subsequent combined images.

Referring to the flow chart of FIG. 6, an explanation will be givenbelow on another example of the sequence of the joining operations thatare carried out on the above-mentioned document data.

Firstly, the joining mode is selected through an operation panel, notshown, (S21), and when some documents are scanned (S22), data readthrough the CCD sensor 6 are stored in the image memory 43 (S23). Suchscanning processes of the documents and storing processes of thedocument data (S22 and S23) are repeated as many times as the number ofimages that are to be joined together until it is determined at S24 thatthe reading operation of the documents has been completed.

After completion of the reading of the documents, when a joiningoperation is instructed (S25), features the documents are extracted byretrieving data corresponding to predetermined lines from the edge ofthe document data stored and recognizing peculiar lines, characters,etc. (S26) thereon.

Then, a check is made to see if the data forming joints coincide witheach other by comparing the features extracted from the respective data(S27). The steps S26 and S27 are carried out in the joint recognitionsection 44. The document data are arranged so as to align the coincidedjoints face to face with each other (S28), and positioning is carriedout so as to get the images smoothly joined together. These steps arecarried out in the data- arranging section 46 and the positioningsection 46. Such processes as the extraction of the features of thedocuments (S26), the judgement on the coincidence of the data (S27), andthe arrangement of the document data (S28) are repeated in theabove-mentioned order until it is determined at S29 that the processingof all the data has been completed. In contrast, if the judgement is"NO" at S27, the document data are not arranged, and the sequenceproceeds to S29. Here, if there are any sides having no coincidence ofdata during the above processes, a flag indicating "no coincidence" isset, thereby executing the joining operation on the rest of the sides.

After completion of all the data processing, a compensating operationfor loss of data is conducted on the sides for which the flag of "nocoincidence" has been set (S30). Then, at S31, a judgement is made as towhether or not the compensating operation for loss of data has beencompleted, and if the compensating operation has been completed, ajudgement is successively made as to whether or not the joiningoperation has been completed, that is, whether or not all the documentdata stored are combined into an image of one sheet (S33). In contrast,if it is determined that the compensating operation for loss of data hasnot completed at S31 or the joining operation has not been completed atS33, a warning display indicating "NO" is given to inform that nojoining process is operable (S32), thereby stopping the operation.

After determination of the completion of the joining operation at S33, ajudgement is then made as to whether or not the size of copy sheetswhereon the combined image is formed is specified (S34). If the size ofthe copy sheets is not specified, copy sheets having the largest sizeamong the copy sheets that are set in the digital copying machine areselected (S35), and a variable magnification operation is carried out inaccordance with the copy sheets having the largest size (S36). Incontrast, if the size of the copy sheets is specified, a variablemagnification operation is carried out in accordance with the size ofcopy sheets that has been specified. Further, conversion of thecoordinates is executed on the document data according to thelongitudinal feeding or the lateral feeding of the copy sheets, ifnecessary (S37), and the subsequent data are released to the laserdriver unit 7, thereby carrying out copying operations of the combinedimage on copy sheets (S38).

Referring to a flow chart in FIG. 7, an explanation will be givenhereinbelow on the extraction of features on the documents in theabove-mentioned joining operation.

Firstly, one side of an image in question is selected (S41), and an areacorresponding to predetermined lines from the end of the selected side,for example, corresponding to several tens of lines inward from the end,is specified (S42). Then, a selection is made to find a best-suitedmethod for making the features clear among methods using thearrangement, pattern, and color tone of the data depending on the imagein question, and features that are present within the feature-extractionarea are extracted (S43), thereby storing the extracted features bydigitizing them (S44).

Successively, one side of a comparative image, which is to be joined tothe image in question, is selected (45), and an area from which featuresare extracted is specified in the same manner as described in the imagein question (S46). Then, the features of the comparative image areextracted in the same manner as described in the feature-extraction ofthe image in question (S47).

Additionally, in the image memory 43, after detecting the size of adocument to be read in accordance with the controlling for the normalimage reading, storing, copying, etc., an address space is provided inthe memory. As shown in FIG. 8, document data are stored therein at arate of one image per page. Therefore, as shown in FIG. 9, each end of adocument (for example, indicated by an area having slanting lines inFIG. 9) can be clearly indicated by an address on the memory, and thefeature-extraction area can be specified in accordance with the area.

As described above, after extracting respective features from the imagein question and the comparative image, a judgement is made as to thecoincidence or non-coincidence of the data by comparing the featureextracted from the comparative image with the feature of the image inquestion that have been stored earlier, as is shown in the flow chart ofFIG. 10.

Firstly, a feature extracted from the image in question is roughlycompared with a feature extracted from the comparative image (S51), anda judgement is made as to whether or not the features compared with eachother coincide with each other within a range of a predeterminedapproximation (S52). If the features almost coincide with each other,the document data are arranged so that the sides having the extractedfeatures are aligned face to face with each other, and positioning isperformed in the image memory 43 so that the arrangement, pattern, colortone, etc. of the data are well suited. In other words, the images arecompensated for their offsets caused when they are read by shifting oneof the images in an up and down direction and in a right and leftdirection (S53 and S55), and also compensated for their tilts caused bythe tilts of the documents when they are read by rotating one of theimages by several degrees (S57).

Moreover, if it is determined that no coincidence is found between thefeatures when the features are roughly compared, or when one of theimages is shifted in an up and down direction and in a right and leftdirection, or when one of the images is rotated (S52, S54, S56, andS58), a judgement is again made as to whether or not the featurescoincide with each other (S60) after one of the images is rotated by180°(S59). If it is determined at S60 that no coincidence is foundbetween the features, one of the images is rotated by several degrees(S61), and even after the rotations, if it is determined that nocoincidence is found between the features (S62), a flag indicating "nocoincidence" is set (S63).

More specifically, since the documents have a rectangular shape in mostcases, their image might be read upside down in an up and downdirection. Therefore, even if no coincidence is found between the imagesin their stored states, the coincidence is again confirmed in the imagememory 43 by rotating one of the images by 180°. Further, taking accountof the case when upon reading, the document is set in a slightly tiltedstate, even if no coincidence is found between the images after makingthe 180° rotation, the features are again compared by rotating one ofthe images by several degrees.

In contrast, if it is determined at S60 and S62 that the featurescoincide with each other, the sequence proceeds to S53, and the shift ofthe images in an up and down direction and in a right and leftdirection, the rotation of the images, etc. are performed as describedearlier so that the arrangement, pattern, color tone, etc. of the dataare well suited, thus making the positioning of the images.

Next, referring to the flow chart of FIG. 11, an explanation will begiven in detail concerning the judgement on the completion of all thedata processing.

If a plan for the joining operation is preliminarily inputted through acertain method upon reading images or other occasions, it is determinedat S65 that there is an inputted plan. In this case, since the sidesforming the ends of images are preliminarily known and since the joiningoperation is not carried out on the sides merely including the ends ofimages, a judgement is made as to whether or not all the data processinghas been completed (S68), by making a check to see if the joiningoperation is being carried out on the other sides (S67).

In contrast, if document data are randomly inputted, that is, if no planfor the joining operation is specified, the judgement is made as "NO" atS65. Therefore, a judgement is made as to whether or not all the dataprocessing has been completed (S68), by making a check to see if thejoining operation is being carried out on the four sides in the data(S66). Additionally, in this case where the document data are randomlyinputted, it is determined that the sides on which no coincidence of thefeatures is found are sides merely forming the ends of images, and thejoining operation is successively carried out on the other sides.

Here, referring to FIG. 12, an explanation will be given on this indetail. For example, if four images a through d are randomly inputted asdocument data, judgements as to the coincidence or non-coincidence ofthe data are made twelve times in the total number: [4 (sheets)×4(times)-4 (sides, where the coincidence is found)=12]. As a result, thejoining operation is carried out on each of the pairs of sides a₄ andb₃, b₂ and d₁, a₂ and c₁, as well as c₄ and d₃, while flags forindicating "no coincidence" are set for the other eight sides merelyincluding the ends of images (a₁, a₃, b₁, b₄, c₂, c₃, d₂ and d₄).

Additionally, in the case of joining torn pieces of a document 65 and66, shown in FIG. 13(a), by using the above-mentioned joining operation,the torn pieces are placed onto the document platen 27 with the torn end65a and 66a aligned face to face with each other in accordance with thepositional relationship before it is torn, as shown in FIG. 13(b), andthe-pieces of the document 65 and 66 are scanned by the scanner unit 22,for example, in the direction of arrow A. This arrangement makes itpossible to perform a quick joining operation.

In this case, during the aforementioned feature-extracting process onthe images, the torn end 65a at the rear end of the document piece 65and the torn end 66a at the leading end of the document piece 66 arerecognized as portions to be joined together. Thus, upon selecting oneside of the image in question at S41, the rear side of the documentpiece 65, which has been scanned earlier, is first selected. Further,upon selecting one side of the comparative image at S45, the leadingside of the document piece 66, which has been scanned later, isselected. Thereafter, the feature-extracting is carried out on the othersides in the same manner.

Moreover, at S51 shown in FIG. 10, comparison is first made between thefeatures of the data representative of the rear side of the documentpiece, scanned earlier, and those of the data representative of theleading side of the document piece, scanned later, and if necessary,comparison is made between the features of the data representative ofthe other sides of the document pieces. In such a process, where thepieces of the document 65 and 66 are placed as shown in FIG. 13(b),comparison is first made between the features of the sides that aresupposed to be coincident with each other. Therefore, it becomespossible to easily compare the features of the other sides with eachother, thereby providing a quick operation.

Furthermore, if a plan for the joining operation is preliminarilyinputted through a certain method, that is, if it has already determinedthat the joining operation is carried out only between the torn ends 65aand 66a of the documents pieces 65 and 66, it is determined at S65 thatthere is an inputted plan. In this case, since the sides forming thejoining ends of the images are already determined and since the joiningoperation is not carried out on the sides merely including the ends ofimages, a judgement is made as to whether or not all the data processinghas been completed. This is done by making a check to see if the joiningoperation is being carried out on the other sides at S66.

After completion of all the data processing as described above, if anyflags for indicating "no coincidence" are found at any portions otherthan the ends of images, a compensating operation for the loss of datais carried out. As to the compensating operation for the loss of data,an explanation will be given with reference to the flow chart of FIG.14.

Firstly, a judgement is made as to the presence or absence of the flagsfor indicating "no coincidence" (S71), and if no flags are found, thesequence proceeds to the step for determining the completion of thejoining operation without executing the compensating operation for theloss of data. In contrast, if the flags for indicating "no coincidence"are found, a check is made to see if the joining operation has beencompleted on each of the other sides (S72). More specifically, if thejoining operation is not applicable due to a certain problem, the flagfor indicating "no coincidence" is set. Therefore, in order to make ajudgement as to whether the cause of the setting of the flag lies in anerror in setting the document, which interrupts the images from beingjoined into one image, or lies in a loss of the image occurred duringthe reading process of the document, a check is made to see if thejoining operation has been completed on each of the other sides.

If it is determined at S73 that the joining operation has not beencompleted on the other sides, it is determined that the setting of theflag is caused by an error in setting the document, and a warningdisplay indicating that no joining operation is possible is given. Incontrast, if it is determined at S73 that the joining operation has beencompleted on each of the other sides, it is determined that the settingof the flag is caused-by a loss of the image, and a check is initiatedon the data-loss area in order to conduct a compensating operation forthe loss of data.

In other words, taking account of the joining operation carried out onthe rest of the sides except the side on which the loss of image issupposed to exist, the check is made to determine the data-loss areaassuming that the position of the image having the data-loss has alreadybeen determined in relation to the other images. Firstly, a side to bejoined to the side having the data-loss is defined as a first line, andscanning in the sub-scanning direction is executed line by line in themain scanning direction until any change appears in the data (S74).Thus, the data-loss area is determined by defining the first line as aas well as defining the line at which a change in the data has firstappeared as b (S75).

For example, if images shown in FIG. 15 are stored in the image memory43 as document data, and if document data 67 containing a loss of datahave been determined in their position in relation to document data 70as well as having been positioned in relation to other document data 68and 69 in accordance with sides 67a and 67b having no data-loss, thestart line for scanning is given by a (the end of the document data 70)and the line at which a change in the data has first appeared isindicated by b; therefore, it is determined that the data-loss area ofthe image corresponds to an area between the lines a and b.

Next, referring to the flow chart of FIG. 16, an explanation will begiven on the creating operation .of compensating data for compensatingfor the data-loss of the images that have been determined as describedabove.

Firstly, the main scanning counter is initialized (S76), and the mainscanning counter counts up to a line where data first appear in the areaon which the above judgement has been made, on one of the document data(S77). Thus, data, for example, corresponding to several tens of linesare retrieved, and a check is made to see the tilt thereof (S78).Successively, a check is made to see if any data of the other documentdata are present in the vicinity of an extended line from the data thathave been confirmed on the tilt thereof (S79). If no data are present,it is determined that no target is identified (S80), a warning displayindicating that no joining operation is possible is given.

In contrast, if data are present in the vicinity of the extended line,the judgement is made as "NO" at S80, and compensating data for thedata-loss area are created so as to connect the document data (S81). Theabove-mentioned steps (S77 through S81) are carried out for one line inthe main scanning direction, and if it is determined at S82 that thecreation of the data has been completed for the one line in the mainscanning direction, the sequence proceeds to the steps for determiningthe completion of the joining operation.

In the decision on the completion of the joining operation, as shown inthe flow chart of FIG. 17, if a plan for the joining operation ispreliminarily inputted, it is determined at S81 that there is aninputted plan, and according to the plan, a check is made to see if allthe data are joined together to form one image in the manner asinstructed (S82). In contrast, if no plan is specified, a check is madeto see if all the data are joined together (S83). Then, if it is notdetermined at S84 that the joining operation has been completed, awarning display indicating that no operation is possible is given, whileif it is determined that the joining operation has been completed, thesequence proceeds to the steps for checking to see if the size of copysheets has been specified. Thereafter, the aforementioned operations,such as the mark-erasing operation, variable magnification operation,coordinates-converting operation, etc., are carried out, thereby copyingthe combined image.

As described above, in the digital copying machine of the presentembodiment, images on torn pieces of a document are automaticallycombined together to form an accurate copy of the original document.Further, since shadows, which occur at portions corresponding to joints,are erased, it is possible to ensure high-quality in the subsequentcombined image.

Moreover, as to torn pieces of a document that are placed on thedocument platen 27 with their torn ends aligned face to face with eachother so as to be successively scanned, assuming that the rear edge ofthe torn piece that has been scanned earlier is joined to the leadingedge of the torn piece that has been scanned later, a judgement is firstmade as to the coincidence or non-coincidence of the rear edge and theleading edge. This makes it easier to make judgements as to thecoincidence or non-coincidence of the rest of the edges of the tornpieces. Further, if the rear edge coincides with the leading edge, thisalso makes it unnecessary to arrange the data by the use of theconversion of the coordinates, or other procedures, because only thenecessary process is a positioning on the data corresponding to theportions in question. Therefore, this arrangement simplifies the joiningoperation as well as shortening the time of the operation. Furthermore,if the joining operation is conducted on, for example, only two tornpieces of a document that are to be joined together at their leading andrear edges, only the necessary processes are a judgement as to thecoincidence or non-coincidence that is conducted according to thefeature-extraction on these leading and rear edges and a positioning ofthe data in question, thereby making it possible to further simplify thejoining operation as well as further shortening the time of theoperation.

Referring to FIGS. 1 and 2 as well as FIGS. 6 through 12, and FIGS. 14through 20, the following description will discuss another embodiment ofthe present invention. Here, for convenience of explanation, thosemembers that have the same functions and that are described in theaforementioned embodiments are indicated by the same reference numeralsand the description thereof is omitted.

As with the digital copying machine described in the aforementionedembodiments, a digital copying machine of the present embodiment, as oneexample of image forming apparatuses, has a structure shown in FIG. 2.Further, the digital copying machine is provided with an imageprocessing section, which has a construction as shown in FIG. 1. Thedigital copying machine of the present embodiment is effective when itis used for executing a joining operation on documents such as thosehaving a margin around the edge of an image or having the same imagesformed in an overlapped manner on the edges of the consecutive pages soas to make clear the connection between the divided portions of animage, for example, in images of a map or the like. More specifically,in the case where there is a margin or there are overlapped images, whendata are successively retrieved from the edge of each document in orderto detect a joint, it takes a long time for retrieving until data havingspecific features are found. In order to solve this problem, the digitalcopying machine of the present embodiment is provided with anarrangement wherein marks having a predetermined color is put ondocuments, and by using the marks, the joining operation is carried outquickly and accurately on such documents as described above.

For example, those marks preliminarily put on the document include:joining lines L₁ which indicate approximate borders for distinguishingnecessary portions from unnecessary portions, that is, approximatepositions at which respective images are joined together, as are shownin FIG. 18; feature-indicating lines L₂ which indicate positions offeatures that coincide with positions at which respective images arejoined together, as are shown in FIG. 19; and enclosing marks M whichindicate positions of features that coincide with positions at whichrespective images are joined together by enclosing the features, as areshown in FIG. 20. These marks are selectively used depending on imageswhich are subject to the operation in question.

In the present digital copying machine, in order to form an image of onesheet by joining together images of a map that are successively carriedon a plurality of pages and that have overlapped portions therein, marksas described above are preliminarily put in the vicinity of edges ofrespective documents 71 through 76 by using a pen in a predeterminedcolor. The marks thus provided are recognized as having a drop color,and erased after completion of the joining operation in the presentdigital copying machine.

The sequence of operations for joining these images read in the dividedmanner to form an image on one sheet is almost the same as thatdescribed in the aforementioned embodiment by reference to the flowchart of FIG. 6. However, in the extraction of the features from thedocuments at S26, if the marks are preliminarily put on the documents,the feature-extraction is carried out in accordance with the marks, andconducted only on the sides having the marks.

Further, in specifying the feature-extraction area at S42, if the marksare preliminarily put on the documents, the selection of the sides andthe specifying of the feature-extraction area are carried out inaccordance with the marks.

More specifically, if joining lines L₁ are provided as shown in FIG. 18,the sides having these joining lines L₁ are selected, and several tensof lines located before and after each joining line L₁ are specified asthe feature-extraction area. Further, if feature-indicating lines L₂ areprovided as shown in FIG. 19, the sides having these feature-indicatinglines L₂ are selected, and an area including the vicinity of eachfeature-indicating line L₂ is specified as the feature-extraction area.Moreover, if enclosing marks M are provided as shown in FIG. 20, thesides having these enclosing marks M are selected, and each enclosingmark M is specified as the feature-extraction area.

Thus, upon selecting one side from the sides of the comparative image atS45, if the mark is provided, the side having the mark is selected.

As described above, in the digital copying machine of the presentembodiment, if marks are preliminarily put .on documents, features ofthe documents are extracted in accordance with the marks. Therefore,sides having no marks are not identified as sides in question since theyare merely recognized as sides merely including ends of images. Further,the feature-extraction areas are specified in accordance with the markswith respect to the sides having the marks. Therefore, in comparisonwith the case where the feature-extracting is started from each end withrespect to all the sides of the document data, the memory capacity canbe saved and the processing time required for extracting the featurescan be shortened. In particular, in the case where thefeature-indicating lines L₂ of FIG. 18 and the enclosing marks M of FIG.19 are put as the marks, since these marks also indicate the position offeatures forming joints, the feature-extraction area can be specified bymerely using the surrounding portions of the feature-indicating lines L₂and the areas enclosed by the enclosing marks M. This makes it possibleto save memory capacity to a great extent.

Also in the judgement as to the coincidence or non-coincidence of thedata (see FIG. 10), if the marks are preliminarily put on the documents,the feature-extraction is made only on the sides having the marks.Therefore, the processing time required for the judgement as to thecoincidence or non-coincidence of the data can be shortened, therebymaking it possible to perform the positioning of the documents morequickly and accurately.

For example, as shown in FIG. 21, the coincidence of data is determinedbetween document data 71a and 72a, and after positioning is performed,the area having the overlapped image (indicated by the area sandwichedby alternate long and short dashes lines) is removed, thereby allowingthe images of the document data 71a and 72a to be smoothly joined.

Further, in the judgement on the completion of all the data processing,upon reading the image or other occasions, if it is possible to clearlydistinguish sides to be joined together from those merely including theends of images through the presence and absence of the aforementionedmarks, it is determined at S65 that there is an inputted plan.

Therefore, after successively reading documents whereon various marks asshown in FIG. 18, FIG. 19 or FIG. 20 are put, the joining operation iscarried out in such a manner that a copy 77 as shown in FIG. 22 can beobtained.

Additionally, in the above joining operation that is carried out on thedocuments having the marks, since the marks thus provided are recognizedas having a drop color, an image from which the marks have been erasedis formed on the resulting copy.

As described above, in the digital copying machine of the presentembodiment, in accordance with the marks that have been preliminarilyput on the documents, the feature-extraction is carried out and thepositioning of the images is carried out, thereby producing a combinedimage on one copy sheet. Therefore, it is possible to save the memorycapacity and to carry out the operation quickly and accurately.

Additionally, in the present embodiment, the explanation has been givenby exemplifying the case where the joining operation is carried out onpages of a map, etc. in the form of a book whereon overlapped images areformed at the vicinity of the edges of the consecutive pages. However,the joining operation of the present embodiment may be applied todocuments, each having margins surrounding an image. Also, in this case,the joining line L₁ is preliminarily put along the border between themargin and the image, or the feature-indicating line L₂ or the enclosingmark M is provided so as to indicate features that are located in thevicinity of the border between the margin and the image. Thus, itbecomes possible to save the memory capacity and to carry out theoperation quickly and accurately.

Referring to FIGS. 2, 3, 6, 10, 23 and 24, still another embodiment ofthe present invention will be discussed hereinbelow.

The digital copying machine of the present embodiment has a constructionshown in FIG. 2, and is provided with the capability to perform thesteps shown in FIG. 3. The digital copying machine is designed toperform a quick joining operation when used in the case where tornpieces of a document 78 and 79, shown in FIG. 23(a), are placed on thedocument platen 27 with their torn ends 78a and 79a aligned face to facewith each other in accordance with the positional relationship before itis torn, as shown in FIG. 23(a), and the pieces of the document 78 and79 are scanned by the scanner unit 22. In this case, the basic operationof the joint-portion processing section is the same as that shown in theflow chart of FIG. 6; yet, the feature- extracting operation of thedocument at S27 of FIG. 6 is shown in FIG. 24. An explanation of theseoperations is given below.

Firstly, the document data stored in the image memory 43 are retrieved,and a judgement is made as to whether or not data representative of ashadow are present between any portions of the document data that seemto be consistent (S91). In this case, if the document pieces 78 and 79are placed with their torn ends 78a and 79a in contact with each otherin accordance with the original positional relationship before it istorn, for example, as shown in FIG. 23(b), a shadow 80 is present alongthis contact portion. Therefore, since data representative of a shadoware present between portions of the document data that seem to beconsistent, the judgement is "Yes" at S91, and the shadow portion isrecognized as a torn end (S92).

Next, one predetermined image is defined as an image in question, whilethe other image that is to be joined to this is defined as a comparativeimage. Thus, one side corresponding to the shadow portion of the imagein question, that is, one side corresponding to the torn end, isselected (S93), and an area corresponding to predetermined lines inwardfrom the end of the selected side is specified (S94). Then, features areextracted in this area (S95), and the extracted features are stored bydigitizing them (S96). Next, one side corresponding to the shadowportion of the comparative image that matches the one side of the imagein question is selected (S97), and an area from which features areextracted is specified in the same manner (S98), thereby extracting thefeatures of this image (S99). Here, the above-mentioned steps S93through S99 correspond to the steps S41 through S47 that have been shownin FIG. 7.

In contrast, at S91, if no data representative of a shadow are presentbetween any portions of the document data, that is, if the documentpieces 78 and 79 are not placed in the state as shown in FIG. 23(b), butplaced unintentionally in a scattered manner, one side of the image inquestion is selected (S100), and its feature-extracting area isspecified (S101). The features of the selected side are extracted byretrieving this area (S102), and the extracted features are stored bydigitizing them (S103). Successively, one side of the comparative imageis selected (S104); its feature-extracting area is specified (S105); andthe features of the selected side are extracted (S106).

Next, at S27 of FIG. 6, which is the same as the judging operation as tocoincidence or non-coincidence in FIG. 10, a judgement is first made asto the coincidence or non-coincidence of the corresponding torn endsthat have been detected by the data of shadow. The processes that arecarried out following S28 and thereafter, shown in FIG. 6, are the sameas those described in the aforementioned embodiment, and the erasingoperation for the data of shadow is carried out in the processes S28 andthereafter.

As described above, also in the digital copying machine of the presentembodiment, images on torn pieces of a document are automaticallycombined together to form an accurate copy of the original document.Further, since shadows, which occur at portions corresponding to joints,are erased, it is possible to ensure high-quality in the subsequentcombined image.

Moreover, as to torn pieces of a document that are placed on thedocument platen 27 with their torn ends in contact with each other inaccordance with the original positional relationship before it is torn,data of a shadow located between portions of document data previouslyread are recognized as torn ends of the document, and a judgement isfirst made as to the coincidence or non-coincidence of the correspondingtorn ends. This arrangement makes it possible to shorten the time of thejudging operation. Further, if the torn ends coincide with each other,this makes it unnecessary to arrange the data by the use of theconversion of the coordinates, or other procedures, because only thenecessary process is a positioning on the data corresponding to theportions in question. Therefore, this arrangement simplifies the joiningoperation as well as shortening the time of the operation. Furthermore,since the torn pieces of a document are placed on the document platen 27with all their torn ends properly in contact with one another, it iscertain that the joining operation is not required for the ends of thetorn document pieces other than the torn ends. Therefore, in the casewhere this fact has been inputted to the joint-portion processingsection 48, only the necessary processes are a judgement as to thecoincidence .or non-coincidence that is conducted according to thefeature-extraction on the corresponding torn ends and a positioning ofthe data in question, thereby making it possible to further simplify thejoining operation as well as further shortening the time of theoperation.

The above-mentioned joining operation will be explained morespecifically by reference to a case where images of six pieces of adocument 81 through 86, for example as shown in FIG. 25, are scanned bythe scanner unit 22, and stored in the image memory 43.

In the case where the above-mentioned input plan is specified, uponreading images, the document pieces are successively scanned in theorder to be joined, and in order to specify a change into a new line inthe image memory 43, a specific document, such as a sheet of whitepaper, is read prior to the document after which the line change ismade. In other words, beginning with the document piece 81 shown in FIG.26(a), the scanning of the images are successively conducted on thedocument piece 82, shown in FIG. 26(b), and on the document piece 83,shown in FIG. 26(c). Here, in order to specify a change into a new line,a sheet of white paper 87, shown in FIG. 26(d), is scanned. Thereafter,the document piece 84, the document piece 85, and the document piece 86,which are respectively shown in FIG. 26(e), FIG. 26(f) and FIG. 26(g),are successively scanned in this order.

With this arrangement, the joining operations are respectively conductedon side A₂ of the document piece 81 and side B₁ of the document piece 82as well as on side B₂ of the document piece 82 and side C₁ of thedocument piece 83. As to the document pieces 84 through 86 that havebeen inputted after the sheet of white paper 87, since the instructionfor changing into a new line is given, they are arranged in the lowerrow under the document pieces 81 through 83 in the image memory 43.Therefore, the joining operations are respectively conducted on side Asof the document piece 81 and side E₄ of the document piece 84, on sideB₃ of the document piece 82 and side F₄ of the document piece 85, aswell as on side C₃ of the document piece 83 and side G₄ of the documentpiece 86. Further, the joining operations are also conducted on side E₂of the document piece 84 and side F₁ of the document piece 85 as well ason side F₂ of the document piece 85 and side G₁ of the document piece 86in accordance with the order inputted.

In the case where document pieces are inputted at random regardless ofthe order of their joining operations, as the number of the documentpieces increases, or as the images become more complicated, the time ofthe operations is prolonged, and the number of errors increases.However, with the above arrangement wherein sides to be joined arepreliminarily specified upon reading the images by the use of the inputorder and the instruction using sheets of white paper, it becomespossible to perform the operations quickly and accurately, even if anumber of document pieces are joined one after another.

Moreover, in an image of document data read by the scanner unit 22, adata-loss portion 67c is quite likely to exist at the end of the imageon the document data 67, as shown FIG. 27(a), due to an offset or otherreasons caused when the document piece is placed on the document platen27. In such a side having the data-loss portion 67c, the joiningoperation is not carried out, and a flag indicating "non-coincidence ofdata" is set. However, even in the case where there is a side at whichthe flag indicating "non-coincidence" is set, if coincidence of data isconfirmed at predetermined points in the document data or if coincidenceof data is confirmed by a level beyond a predetermined amount, thepositioning of the document data 67 is carried out in relation to theother sides having no data-loss portion. Therefore, in accordance withthe positioning, compensation for data is executed on an area betweenlines a and b, which is determined as a data-loss area in the manner asdescribed earlier.

More specifically, as illustrated in FIG. 27(b), a compensating-datacreating process is carried out so that images are smoothly joinedtogether between the lines a and b having a distance Δh by compensatingfor an offset Δw between the images in the document data 67 and thedocument data 70. Thus, compensated data as shown in FIG. 27(c) iscreated, thereby carrying out the compensating operation for the loss ofdata.

Additionally, in such a compensating-data creation, the same process iscarried out not only in an up and down direction with respect to theabove-mentioned lines a and b, but also in a right and left direction.

Moreover, as illustrated in FIG. 28, a line 88 is quite likely to appearat a portion corresponding to the edge of the document in the documentdata 67 stored in the image memory 43. Therefore, the digital copyingmachine in the present invention is provided with a function forrecognizing such a line 88 when the document data 67 are inputted to theimage memory 43 and for erasing the line 88 caused by the edge of thedocument.

An explanation will be given on a method for discriminating a linecaused by the edge of a document P from its image, for example, byreference to a case where the document P is placed along a documentguide 27a that is installed on the document platen 27, as illustrated inFIG. 29. Assuming that the document P is set with its edge facing thedocument guide 27a as illustrated in FIG. 30(a), a portion correspondingto the document guide 27a has a white level, and the next portioncorresponding to the edge of the document P has a black level, and thenthe image area of the document is scanned, as illustrated in FIG. 27(b).Therefore, an area located between a changing point (x) from the firstwhite level to the black level and the next changing point (y) at whichthe white level is recovered is determined to be an edge of thedocument, and the edge is erased by replacing the area between x and ywith the while level, as illustrated in FIG. 30(c).

Further, as illustrated in FIG. 29, there is a possibility that thedocument P may be set with a slight offset from the document guide 27a;this causes the edge of the document P to tilt with respect to the mainscanning direction, that is, to become unparallel to the main scanningdirection. Therefore, the discriminating process for the edge of thedocument by the use of the level changes is carried out for each dot,line by line in the main scanning direction.

Here, in the above explanation, the explanation has been given on thecase where the image area starts with a white level; yet, also in thecase where the image area starts with a black level, one portion of theimage is erased. Therefore, the above-mentioned compensating process iscarried out in the main scanning direction, thereby compensating for theloss of data.

In the case where all the edge of the document starts with a blacklevel, the edge-erasing process is operable by preliminarily determiningan area corresponding to predetermined lines from the end of thedocument data as an edge portion of the document. Here, theabove-mentioned lines are determined depending on a design of an opticalsystem in the digital copying machine, the thickness of a copy sheet, orother factors, and they are changeable through a simulation setting.

Furthermore, in the document data stored in the image memory 43, thereis also a possibility that upon reading images, the images are inputtedwith some overlapped portions. For this reason, the digital copyingmachine in the present embodiment is provided with a function forrecognizing the overlapped portions and for compensating for them. Inother words, upon conducting the aforementioned feature-extractingoperation on document pieces, if, as a result of search conducted ondata corresponding to predetermined lines, coincidence of data is foundnot at the end of the document data, but inside the document data, anarea corresponding to lines located outside from the line of the datacoincidence is determined as an overlapped portion of the images.

For example, as illustrated in FIG. 31, if there is an overlappedportion between document data 89 and 90, a line in FIG. 31 (indicated byan alternate long and short dashes line) of the document data 89 becomescoincident with the line of the data at the end of the document data 90;therefore, an area 89a located outside the line is determined to be anoverlapped portion. Then, this overlapped portion of the images iserased, and as illustrated in FIG. 32, positioning is carried out byshifting one of the document data so that the data corresponding to theline in the document data 89 coincide with the data at the end of thedocument data 90. Here, due to this compensating process for theoverlapped portion, a loss of the image appears at the side opposite tothe side having been subject to the compensation in the document data.Therefore, the aforementioned compensating operation is carried out onthe loss of data, thereby compensating for the loss of data.

As described above, by suitably performing, on demand, compensatingprocesses for loss of data and overlapped portions of images, erasingprocess for lines corresponding to the edge of a document, or otherprocesses with respect to document data stored in the image memory 43, acopy 91 with no problems seen at its joined portions can be obtained asshown in FIG. 33. Further, by inserting a sheet of white paper forspecifying a change into a new line during image reading, it becomespossible to perform the joining operation quickly and accurately even ifcomplicated images are used, or even if a number of documents are read.Moreover, merely by specifying the size of copy sheets to be used forcopying the combined image, a variable magnification operation isautomatically conducted, thereby eliminating the need for troublesomecalculations.

Referring to FIGS. 1 and 2 as well as FIGS. 34 through 38, the followingdescription will discuss another embodiment of the present invention.Here, for convenience of explanation, those members that have the samefunctions and that are described in embodiment 1 are indicated by thesame reference numerals and the description thereof is omitted. Further,as with the digital copying machine described in Embodiment 1, a digitalcopying machine of the present embodiment has a structure shown in FIG.2, and an image processing section, which is installed in the digitalcopying machine, has a construction as shown in FIG. 1.

In the above-mentioned digital copying machine, it is arranged that avoid area B and image losses Ia and Ib are formed along the side portion99a and the leading portion 99b of a copy sheet 99 as shown in FIG. 34.These areas are provided in order to improve the picture quality, andtheir function is to prevent lines and stains located along the edge ofa document from being copied on a copy sheet.

As to the side portion 99a on the copy sheet 99, the void area B, whichis a space portion free from adhesion of toner on a copy sheet 99, isformed by erasing portions of a latent image located at the side edge ofthe circumferential surface of the photoreceptor drum 10 by the use of avoid lamp (not shown) so as not to make toner contact with a region onthe copy sheet 99, with which separation claws (not shown), whichseparate the copy sheet 99 from the transferring belt 17 (see FIG. 2)after a toner image having been transferred thereonto, come intocontact. Further, in some cases, a void area is formed at the leadingportion 99b of the copy sheet 99 due to a blank lamp (not shown) that isused for eliminating charge at non-image region depending on its timingof turning-on.

On the other hand, the image losses Ia and Ib, which are formed throughthe timing of scanning start and the on-timing of a resist roller,represent portions at which the image has not been copied at the edge ofthe copy sheet 99 due to an offset between the image forming positionsof the document 92 and the copy sheet 99. The side image loss Iaincludes a portion of the void area B.

Therefore, in the case when one sheet of a document is made by trimmingand sticking together copied sheets bearing divided portions of theimage of the document, if the image has any loss of image due to thevoid area B and the image losses Ia and Ib, there arise problems thatjoined portions of the divided images look unnatural and the combinedimage becomes shrunk.

In the case of the aforementioned embodiments, since a joiningprocessing of divided document data read by the image processing sectionis carried out before the formation of the latent image on thephotoreceptor drum 10, it is possible to avoid loss of the image due toirradiation by the void lamp, etc. Therefore, in comparison with theconventional case where one sheet of a document is made by trimming andsticking together divided portions of the image, the occurrence ofdata-loss at the joint portions can be reduced.

However, even in this case, there is a possibility that the loss of datamight occur in the document data read by the scanner unit 22 due tooffsets of the timing of scanning start, etc. Therefore, it isimpossible to completely prevent the problems that joined portions ofthe divided images look unnatural and the combined image becomes shrunk.

In order to solve the above problems, the digital copying machine of thepresent embodiment is provided with a function by which even if there isany loss of data in the document data read by the scanner unit 22, theloss of data would be compensated for, and the picture quality is thusimproved.

Next, referring to FIGS. 35 through 38, an explanation of the joiningprocessing of images with the compensation for loss of data will begiven in detail hereinbelow. Here, as to the sequence of the operationsfrom reading document data by the scanner unit 22 to releasing theprocessed document data to the laser driver unit 7, the same operationsas the aforementioned embodiments are carried out except for thecompensation processing on the loss of data.

Suppose that two portions of image data 93 and 94, for example, shown inFIG. 35, are stored in the image memory 43 (see FIG. 1) installed in theimage processing section, and that there are data-loss portions 93b and94b of the image on the sides 93a and 94a that form joining edges of theimage data 93 and 94.

As to these two portions of image data 93 and 94, data corresponding topredetermined lines along the edge of each portion of data 93, 94(indicated by regions having slanting lines) are retrieved so as tocheck out the presence or absence of image data, and joints of the imageare thus recognized. Then, the document data are arranged so that thesides 93a and 94a having the joints of the image are aligned face toface with each other. Here, the predetermined lines that are subject tothe retrieving are set to a range that exceeds the data-loss portions ofthe image.

Thereafter, as shown by a flow chart in FIG. 36, a detection is made asto how many joints there are along the sides having the image data, andat S111, a judgement is made as to whether or not there are two or moreof those joints.

If there is one joint, the judgement is made as "NO" at S111, and apositioning is executed by shifting the data in a right and leftdirection (S112). In other words, as shown in FIGS. 37(a) and 37(b),with one portion of the document data 95 maintained in a fixed state,the other portion of the document data 96 is shifted in a right and leftdirection, thereby searching for the best-suited position for the joint.

If there are two or more joints along the sides having the image data,the judgement is made as "YES" at S111, as shown in FIG. 36. Then, apositioning is executed by shifting one portion of the document data inparallel with the joints, that is, in a right and left direction in thedrawing, while the other portion of the document data is maintained in afixed state (S113). Thus, after finding a position where offsets of theimage data at the joints become virtually equivalent, the shifting ofthe document data in the right and left direction is fixed at theposition.

The above-mentioned position where the offsets become virtuallyequivalent is found as follows: distances between predeterminedpositions of the joints on the image data, for example, distancesbetween the ends of the joints on the image data, are successivelydetected; the distances between the portions of the document data arecompared with each other, for example, in sequential order beginningwith the nearest ones; and a search is made so as to find a positionwhere the offsets of the compared distances on the image data betweenthe portions of the document data become equivalent to each other.

Next, with one portion of the document data maintained in a fixed state,the other portion of the document data is shifted in a virtuallyperpendicular direction to the joints, for example, in a departingdirection in the drawing. Thus, the distance between the portions of thedocument data is widened, and the corresponding edges of the ends of theimage data at the joints are connected by a straight line, that is,hypothetical lines are extended from the corresponding edges of the endsalong the edges (S114).

Then, a search is made so as to find a position where the connected lineand the image are aligned in one straight line, that is, so as to find aposition where the hypothetical lines become virtually coincident witheach other (S115), and the corresponding color is applied between theboth portions of the document data in accordance with the joints. Inother words, the compensating operation for the loss of data iscompleted by applying the corresponding color so as to maintain theconsistency of the image data between the hypothetical lines (S116).

Referring to, for example, FIG. 38(a), a detailed explanation of theabove processing is given below. Suppose that the position of theportions of the document data 97 and 98 are determined in its right andleft directions by making equivalent the offsets of the positions of thecorresponding joints in the portions of the document data 97 and 98.While the distance between the portions of the data is being widened byshifting the portion of the document data 97 away from the portion ofthe document data 98, the corresponding ends of the joints are connectedby straight lines or the like (indicated by broken lines in thedrawing), as is illustrated in FIG. 38(b).

Then, as illustrated in FIG. 38(c), a search is made so as to find aposition where the straight lines connecting to the corresponding endsof each .joint coincide with the image on the portions of the documentdata 97 and 98, that is, so as to find a position where the abovestraight lines and straight lines on the image of the portions of thedocument data 97 and 98 are aligned in respective straight lines.

Here, as illustrated in FIG. 38(d), if the portion of the document data97 is shifted too far away from the portion of the document data 98 topass by the position at which the coincidence of the straight lines ismade, the portion of the document data 97 is shifted closer to theportion of the document data 98, thereby finding the best-suitedposition.

After completion of the compensating operation for the loss of data, thedocument data is subject to the variable magnification processing, thedensity processing, etc. as have been described in Embodiment 1, and isreleased to the laser driver unit 7 so as to form a combined image onone copy sheet.

As described above, in the present embodiment, even if any loss of dataappears in an image upon reading the data of documents, the function forcompensating the loss of data is provided therein to solve the problem.A combining operation is carried out by detecting the joints of thedocuments, and the combined image is formed by executing a variablemagnification operation to a desired size of copy sheet; therefore, aswith the advantages of the aforementioned embodiments, it is possible toimprove the efficiency of work by eliminating extra jobs, and it is alsopossible to enhance the picture quality by eliminating shrinkage ofimages and unnatural appearance of the joints.

Referring to FIG. 2 as well as FIGS. 39 through 41, the followingdescription will discuss another embodiment of the present invention.Here, for convenience of explanation, those members that have the samefunctions and that are described in Embodiment 1 as well as Embodiment 2are indicated by the same reference numerals and the description thereofis omitted. Further, as with the digital copying machine described inEmbodiment 1 as well as Embodiment 2, a digital copying machine of thepresent embodiment has a structure shown in FIG. 2, and an imageprocessing section, which is installed in the digital copying machine,has a construction as shown in FIG. 39.

In the above-mentioned digital copying machine, if a document which islarger than the maximum size of copy sheets available is used forcopying operation, the following procedures are required: first, thedocument is divided into portions, and reduced copying operations areconducted on the respective portions; then, a combined document is madeby trimming and sticking together the reduced portions; and the combineddocument is again copied.

However, the density of each reduced copy varies depending on thedensity distribution of the document during the reduced copyingoperations. Consequently, after the reduced copies have been combinedtogether, the single combined document has different densities on itsrespective portions. This results in unnatural appearance in the Jointportions.

Further, in the case when a book having a considerable thickness, suchas a bound book composed of, for example, annual issues of a scientificmagazine, is opened and placed on the document platen, and when a singledocument is made by copying some pages of the book, the copied pagestend to be tilted depending on the pages, because the bound portion ofthe book is separated from the document platen, or due to the distortionof the opened book. Moreover, in the case when a number of documentssuch as consecutive maps are read out and then combined together, uponreading out the documents forming respective portions, there is apossibility that some documents might be placed on the document platenin a tilted manner, for example, in the wrong orientation of 90° or inthe completely opposite orientation of 180°, and might be read out asthey are.

In the case where such pages and documents are scanned for copying andthe copied portions are then combined together, there arises a problemthat their joined portions might not fit well. The joint-portionprocessing in the positioning section 46 of the aforementionedembodiments has failed to solve the problem.

Therefore, as illustrated in FIG. 39, in addition to the joint-portionprocessing section 48 shown in FIG. 1, the image processing section ofthe present embodiment is provided with: a data-loss/joint/redundancycorrection section (rotative movement means) 100 to which signals fromthe positioning section 46 are inputted; and a density compensationsection (adjusting means) 101 for receiving signals from thedata-loss/joint/redundancy correction section 100 and for releasingsignals to the combination-processing section 47.

In the data-loss/joint/redundancy correction section 100, a positioningof two portions of document data is carried out by rotating one portionof the document data around a predetermined position, such as a centralposition when seen after printing the document data, a center positionof the bound portion of a book, or an end of the bound portion, that is,the corner of a joint of the document data.

Further, as with the positioning section 46 of the aforementionedembodiments, the data-loss/joint/redundancy correction section 100conducts correcting operations on loss of data and redundant portions ofthe joints.

More specifically, after making a rotative movement as described above,if any loss of data or redundant portion is detected, one portion of thedocument data is further shifted in the direction parallel or verticalto the joint, or in the main scanning direction or in the sub scanningdirection so that the image data on the portions of the document databecome virtually consistent. Then, the loss of data at the joint can becompensated for and the redundant portion can be eliminated.

In the density compensation section 101, the density data of the imageand the background in the portions of the document data, which arereleased from the data-loss/joint/redundancy correction section 100, arecompared with one another, and the density data are converted so thatdensity variations between the portions of the document data at thejoint, when seen after printing, can be reduced to a minimum.

Referring to FIGS. 2 and 39, an explanation will be given on thesequence of the joint processing operations on the document data thatare carried out by using the above-mentioned image processing section,in accordance with a flow chart of FIG. 40.

Firstly, the joining mode is selected through an operation panel, notshown, (S121), and when a few pages of divided documents are scanned(S122), data read through the scanner unit 22 are stored in the imagememory 43 (S123).

Successively, joints in the respective images of read data of thedocuments are detected by the joint-recognition section (S124). In otherwords, the position of data of each document is first recognized, andthe edges of data of each document is then recognized. Thereafter, eachedge is examined so as to identify which edge has data by retrievinglocal data corresponding to predetermined lines from the edge of data ofeach document. As to the presence or absence of image data, judgement ismade based on whether or not the value of data (the value of density ineach color) is zero.

Then, at S125, a judgement is made as to the presence or absence ofdetection of joints. If no joint is detected, that is, if there is noedge portion having image data in the data of a document in question,for example, if no joint is detected after making a search by rotatingthe document data from 0° to 180° clockwise as well as counterclockwise,a warning display indicating "NO" is given to inform that no joiningprocess is operable (S126), thereby stopping the operation.

In contrast, if there is a detection of joints at S125, the judgement ismade as "YES", and the data of the documents are arranged by thedata-arranging section 45 so that corresponding edge portions havingimage data are aligned face to face with each other (S127).

Next, a positioning is carried out in the positioning section 46 asfollows: A position where the image data in the portions of the documentdata become consistent within a predetermined range is found whileshifting the second document data, that is, the data of one document, inthe main scanning direction or in the sub scanning direction as well asin the direction parallel to the joint or in the direction vertical tothe joint, with the first document data, that is, the data of the otherdocument maintained in a fixed state. In other words, the best-suitedposition where the joints are connected to each other most smoothly isfound by detecting a position where the image data in the portions ofthe document data are consistently connected within a predeterminedrange (S128).

Successively, a positioning is carried out in thedata-loss/joint/redundancy correction section 100 as follows: A positionwhere the image data in the portions of the document data becomeconsistent within a predetermined range is found while rotating thesecond document data clockwise or counterclockwise around apredetermined position, with the first document data maintained in afixed state. In other words, the best-suited position where the jointsare connected to each other most smoothly is found by detecting aposition where the image data in the portions of the document data areconsistently connected within a predetermined range (S128).

Additionally, at S128, if no consistency is detected within thepredetermined range, the rotative movement is made so that the offsetsof the distances on the image data between the portions of the documentdata become equivalent to each other. Then, as with S113 through S116 inthe aforementioned embodiment, the portions of the document data areshifted, and correcting and compensating operations for loss of data aswell as eliminating operation for redundant portions are conducted attheir joints.

Thereafter, the density of the second document data is converted by thedensity compensation section 101 so that the density of the image of thesecond document data becomes coincident with the density of the imagethat is located on a side having image data of the first document data(S129). Further, the density of the background of the second documentdata is also converted by the density compensation section 101 inaccordance with the density of the background of the first document dataso that besides the images, both of the densities of the backgroundsbecome coincident to each other (S130). Then, the portions of thedocument data are combined to form combined document data to be copiedon a single sheet.

Next, at S131, a judgement is made as to whether or not the size of copysheets for use in printing the combined document data is specified. Ifthe size of the copy sheets is not specified, the judgement is made as"NO", thereby selecting copy sheets having the largest size among thecopy sheets that are set in the digital copying machine (S132), and avariable magnification operation, that is, enlargement, reduction, etc.,is conducted on the combined document data in accordance with copysheets having the largest size (S133).

In contrast, if the size of the copy sheets is specified, the judgementis made as "YES" at S131, and a variable magnification operation iscarried out in accordance with the size of copy sheets that has beenspecified (S133). Further, according to the longitudinal feeding or thelateral feeding of the copy sheets, conversion of the coordinates isexecuted on the combined document data that have been subjected to thevariable magnification operation, if necessary, and the subsequent dataare released to the laser driver unit 7, thereby carrying out copyingoperations of the processed image on copy sheets (S134).

Referring to FIG. 41, an explanation of the above processing is given indetail hereinbelow. In the case when two portions of document data 102and 103 are respectively stored in the image memory 43, as is shown inFIG. 41(a), data corresponding to predetermined lines from the edge ofof each portion of document data 102, 103, which is representative of aside when printed, are retrieved so as to detect the presence or absenceof image data, and sides 102a and 103a having image data 102b and 103bare thus detected.

If the sides 102a and 103a having the image data 102b and 103b of thedocument data are not adjacent to each other, the document data 102 and103 are arranged so that the sides 102a and 103a having the image data102b and 103b are aligned face to face with each other. In this case,for example, the document data 103 is successively rotated from 0° to180° clockwise as well as counterclockwise with a predeterminedinterval. Then, concerning sides that are brought adjacent to each otherwhen rotated, detection is made as to the presence or absence ofconsistent sides 102a and 103a as well as consistent image data 102b and103b, and at the position where those consistencies are seen, thedocument data 103 are arranged.

Then, as illustrated in FIG. 41(b), with one of the portions of thedocument data 102 maintained in a fixed state, the best-suited positionof the image data where the image data 102b and 103b are suitably joinedtogether is found by checking the consistency of the data in apredetermined range while rotating the other portion of the documentdata 103 around a predetermined position clockwise as well ascounterclockwise little by little. Thus, the portions of the image arecombined together to form document data to be copied on one sheet.

If no consistencies are detected, correcting and compensating operationsfor loss of data as well as eliminating operation for redundant portionsare conducted, as described earlier, and the image data 102b and 103bare combined to form combined document data to be copied on one sheet.Thereafter, the combined document data are subject to a variablemagnification processing in accordance with the size of copy sheets tobe used, and conversion of the coordinates is executed, if necessary,thereby producing a reduced copied image 104, as shown in FIG. 41(c).

As described above, in the digital copying machine of the presentembodiment, density adjustments can be conducted so that the densitiesof image and background between respective document data to be joinedare made coincident to each other. Thus, variations of density between ajoint can be reduced to a minimum, thereby making it possible to ensurehigh-quality in the subsequent combined images. Additionally, theabove-mentioned density adjusting process can he applied to theaforementioned embodiments.

Furthermore, the above-mentioned arrangement makes it possible tocompensate for inconsistency of image that is caused by tilt of an imagedue to separation of a document surface from the document platen, whichoften occurs upon copying a thick book, or other reasons, and that isalso caused by wrong orientation of a placed document. Therefore, it ispossible to reduce distortion of image that occurs between joineddocument data; this leads to reduction of distortion of copied imagethat are joined, thereby ensuring copies with better sharpness.Additionally, the above-mentioned positioning process for positioningdocument data while rotating the document data as described above, canbe applied to the aforementioned embodiments.

Referring to FIG. 2 as well as FIGS. 42 through 50, the followingdescription will discuss another embodiment of the present invention.Here, for convenience of explanation, those members that have the samefunctions and that are described in the aforementioned embodiments areindicated by the same reference numerals and the description thereof isomitted.

As with the digital copying machine described in the aforementionedembodiments, a digital copying machine of the present embodiment, as oneexample of image forming apparatuses, has a structure shown in FIG. 2.Further, the digital copying machine is provided with an imageprocessing section, which has a construction as shown in FIG. 42. Theimage processing section is provided with the first and second imagememories (storage means) 105a and 105b, and different document data readby the CCD sensor 6 are respectively stored in the first and secondimage memories 105a and 105b through a switch 107. Here, those imagememories are not limited to the above construction, and any constructionmay be employed as long as it is capable of storing two or more portionsof document data.

The first and second image memories 105a and 105b are connected to adocument-position recognition circuit (joint-portion processing means)106 which conducts predetermined processing such as a shadow erasingoperation and a positioning positioning, which will be described later,on the document data stored. The document data, which have beensubjected to the predetermined processing in the document-positionrecognition circuit 106, are successively released from the first andsecond image memories 105a and 105b to a τ-correction section 49 throughthe switch 108. Here, the other constructions except for theabove-mentioned construction are the same as those of the imageprocessing section that is provided in the digital copying machine ofthe aforementioned embodiments.

When a copy is made from a book or the like having a considerablethickness, shadows are sometimes made because the bound portion of thebook tends to separate from the document platen 27 (see FIG. 2) due toits thickness. The shadows form black portions in the copied image,thereby reducing the resolution of the image. Further, the occurrence ofthose shadow portions gives an adverse effect on the joining processingof a plurality of documents as described in the aforementionedembodiments.

Conventionally, in order to erase shadow portions that are caused by theseparation of a document from the document platen 27 as described above,coping machines which have a "shadow-erasing" function for erasing oneportion of a document image in a uniform manner have been suggested.However, such a shadow-erasing processing causes other problems thatshadow portions would not be completely erased and images that are notshadow portions might be erased; therefore, it is difficult to executeaccurate joining processing.

Therefore, the digital copying machine of the present embodiment isprovided with a function for accurately conducting the above-mentionedshadow-erasing processing as well as for compensating loss of data thatis caused by the shadow-erasing processing.

There are two methods for storing images carried on two opened pages ofa book or the like in the image memories 105a and 105b: one is to storethe document data in the different memories for the respective pages byscanning the pages of the document one by one; and the other is to readthe images of the two opened pages through one scanning, and afterscanning, the resulting document data are divided into two portions onthe image memory basis in accordance with detection results of thedocument size, etc. In this embodiment, assuming that the former methodis used, an explanation will be given exemplifying a case where twoopened pages of a map 109 in the form of a book of B5-size as is shownin FIG. 43(a), by reference to the flow chart of FIG. 44.

When a copying operation is carried out-with the joining mode selected,a document image on a left page 110 is read out, and stored in the firstimage memory 105a (S131). Successively, a document image on a right page111 is read out, and stored in the second image memory 105b (S136).Thus, by reading out the left and right pages 110 and 111 of the openedpages of the map 109 through the individual scanning, the image on theleft page 110 is stored in the first image memory 105a as the firstdocument data 112, as shown in FIG. 43(b), while the image of the rightpage 111 is stored in the second image memory 105b as the seconddocument image 113 as shown in FIG. 43(c).

In this case, along areas of image ends corresponding to the boundportion of the map 109 in the respective document data 112 and 113,shadows 114 are formed respectively due to the thickness of the map.Next, before carrying out erasing operations of the shadows 114, thedocument data 112 and 113 are temporarily stored in a work memory sothat the shadow-erasing operation to the first image memory 105a and theshadow-erasing operation to the second image memory 105b are executed ina common manner. Additionally, the work memory is included in theaforementioned document-position recognition circuit 106 (see FIG. 42).

When the first document data 112 stored in the first image memory 105aare copied to the work memory (S137), the shadow-erasing operation isexecuted on the first document data (S138). Here, if the coordinates onthe image memories 105a and 105b are set as shown in FIG. 45, aneffective image area (an area corresponding to the size of one page) onthe first image memory 105a is indicated by 0 to X1 in the X-coordinateand by Y1 to Y2 in the Y-coordinate. Moreover, the X-coordinate of animage end adjacent to the shadow 114 is indicated by Xs. When theshadow-erasing operation is conducted, the coordinate Xs is stored inthe memory array of Xs1 (S139). After completion of the shadow-erasingoperation, the first document data 112 are copied from the work memoryto the first image memory 105a (S140).

Next, the second document data 113 stored in the second image memory105b are copied to the work memory in the same arrangement as the firstdocument data 112 (S141), and the shadow-erasing operation is executedon the second document data 113 (S142). Moreover, the X-coordinate, Xs,of an image end adjacent to the shadow 114 in the second document data113 is stored in the memory array of Xs2 (S143). After completion of theshadow-erasing operation, the second document data 113 are copied fromthe work memory to the second image memory 105b (S144). Here, theX-coordinates indicating the image ends stored in the memory arrays Xs1and Xs2 are used upon conducting a positioning operation and acompensating operation for a loss of image due to the shadow-erasingoperation, which will be discussed later.

After completion of the shadow-erasing operations, density distributionsare found on the connecting portions 112a and 113a of the first andsecond document data 112 and 113 as shown in FIGS. 46(a) and 46(b), andcorrelation coefficients, which will be discussed later, are calculated,thereby providing the amounts of offset between the respective portions,that is, the amounts of positioning (S145). Successively, as to theportion from which the shadows 114 have been erased, the compensatingoperation is carried out because the document image has also been erasedfrom the portion (S146). In this operation, the colors and densities ofthe corresponding portions between the first and second document data112 and 113 are detected so that both of the data 112 and 113 are joinedto each other smoothly.

Thereafter, the data thus joined to each other are subject to thevariable magnification operation in accordance with the size of copysheets specified (S147), and the data stored in the first and secondimage memories 105a and 105b are successively sent to the laser driverunit 7 with reference to the positioning amounts, thereby executing acopying operation as was described in the aforementioned embodiments(S148).

Next, referring to a flow chart in FIG. 47, an explanation of theshadow-erasing operation will be given in detail.

Firstly, ranges of shadow are detected within the effective image rangesof the image memories 105a and 105b. For example, in the case of theimage memory 105a, assuming that the coordinates from which thedetection is initiated correspond to the coordinates (X1, Y1) of the endof the effective range of shadow (S151), a judgement is made as towhether or not these coordinates fall on a black picture element (S152).If it is determined that the coordinates fall on a black pictureelement, the X-coordinate is shifted to X-1 by one line (S153), and thestep S152 is repeated. At the time when a non-black picture element isfound at S152, it is determined that the range of shadow has beenfinished at line Y1, thereby storing the subsequent coordinate Xs [Y] inthe memory array (S154). Thus, the position at which the shadow has beenfinished at Y1 of the Y-coordinate is stored with respect to theX-coordinate.

Thereafter, a judgement is made as to whether the Y-coordinate hasreached Y2 (S155), and if it has not reached Y2, the Y-coordinate isshifted to Y+1 by one line (S156), the detection of non-black pictureelement is again carried out by scanning the image successively in theX-direction from X1 (S152 and S153), thereby storing in the memory arraythe subsequent X-coordinate at which the shadow has been finished atline Y+1 (S154). The above process is repeated until the Y-coordinatehas reached Y2, that is, until it has been determined that Y Y2 isnegative. Thus, the range of shadow is successively detected from Y1 toY2 line by line with respect to the Y-coordinate.

Additionally, the coordinate Xs [Y] indicating the detection ofnon-black picture element is stored in the memory array of Xs1 when theshadow-erasing operation is carried out with respect to the firstdocument data 112, while it is stored in the memory array of Xs2 whenthe shadow-erasing operation is carried out with respect to the seconddocument data 113.

Next, the shadow-erasing is executed by replacing the picture elementslocated within the range of shadow that has been detected as such withwhite picture elements. In other words, beginning from the end (X1, Y1)of the effective image range (S157), the corresponding coordinate isreplaced with a white picture element as long as X>Xs [Y] is positive atS158, that is, until the corresponding X-coordinate has reached Xs [Y](S159) while repeating the process of shifting the X-coordinate to X-1by one line (S160). With this process, the picture elements that havebeen determined as shadow are replaced with while picture elements inrelation to line Y1, thereby permitting the shadow to be erased.

When the X-coordinate has reached Xs [Y], that is, upon havingdetermined that X>Xs [Y] is negative at S158, the process wherein thecorresponding picture element determined as shadow is successivelyreplaced with a white picture element is repeated line by line withrespect to the Y-coordinate (S158-S160). The process is executed whilerepeating the process of shifting the Y-coordinate to Y+1 by one line(S162) as long as Y<Y2 is positive at S161, that is, until thecorresponding Y-coordinate has reached Y2 (S162). Then, when thereplacement to the white picture element is completed at Y2 of theY-coordinate, that is, upon having determined that Y<Y2 is negative atS161, the replacing process to the white picture element that hasstarted from the coordinates (X1, Y1) is completed, thereby finishingthe shadow-erasing operation.

Next, referring to the flow chart of FIG. 48, an explanation of theprocedure for finding the amounts of positioning of the first and seconddocument data 112 and 113 stored in the first and second image memories105a and 105b will be given hereinbelow. Here, in this explanation, inorder to distinguish the coordinate Xs [Y] that has been stored in thememory array during the shadow-erasing operation depending on the firstimage memory 105a and the second image memory 105b, the Xs [Y] of thefirst image memory 105a is indicated by Xs1 [Y], and the Xs [Y] of thesecond image memory 105b is indicated by Xs2 [Y].

The Y-coordinate is first set to Y1 (S170), and while referring to thecoordinate Xs1 [Y] of the image end that have been stored in the memoryarray of the first image memory 105a, the density of the coordinates ofan image end that have not been subject to the shadow-erasing operationis stored in DN1 [Y] (S171). Next, while referring to the coordinate Xs2[Y] of the image end that have been stored in the memory array of thesecond image memory 105b, the density of the coordinates of an image endthat have not been subject to the shadow-erasing operation is stored inDN2 [Y] (S172). Next, the steps S171 through S173 are repeated byshifting the Y-coordinate to Y+1 line by line (S173) until theY-coordinate exceeds Y2, that is, until it has been determined that Y>Y2is positive at 64. Thus, density distributions in the Y-direction of theimage ends that have not been subject to the shadow-erasing operationare formed in DN1 and DN2 respectively in the document data 112 and 113stored in the first and second image memories 105a and 105b.

When it is determined that Y>Y2 is positive at S174, the amount ofpositioning Z is first set to-50 (S175), and the correlation coefficientof DN1 [Y] and DN2 [Y+Z] is calculated, and stored in R [Z] (S176).Successively, while shifting is made line by line using Z =Z+1 (S177),the steps S176 and S177 are repeated until Z reaches 50, that is, untilit has been determined that Z >50 is positive at S178. If it has beendetermined that Z>50 is positive at S178, the value of Z that is themaximum among values of R [Z] obtained within the range from Z=-50 to 50is found (S179), thereby completing the calculations of the amounts ofpositioning.

Next, referring to the flow chart of FIG. 49, an explanation of theprocedure for compensating for a loss of image that is caused by theshadow-erasing operation is given hereinbelow. Here, in FIG. 49, inorder to distinguish the coordinates Y in the first image memory 105aand the second image memory 105b, the Y-coordinate of the first imagememory 105a is indicated by Y, and the Y-coordinate of the second imagememory 105b is indicated by Yt.

Firstly, it is set that Y=Y1 (S181), and since Yt has an offsetcorresponding to the amount of positioning, Z, from Y, Yt of the secondimage memory 105b that is to be joined to Y1 of the first image memory105a is found by setting Yt=Y+Z (S182). A judgement is made as towhether the subsequent Yt has exceeded the effective image range (Y1 toY2), and if the Yt has exceeded the effective image range, the followinglimiting process is carried out. In other words, if it is determinedthat Yt is smaller than Y1 at S183, it is set that Yt=Y1 (S184), whileif it is determined that Yt is greater than Y2 at S185, it is set thatYt=Y2 (S186).

After completion of the above limiting process that has been carried outin accordance with the judgement whether or not the value of Yt isincluded within the effective image range, the difference D between thedensity DN2 [Yt] of image end in the second image memory 105b and thedensity DN1 [Y] of image end in the first image memory 105a is found byreference to Xs1 [Y] and Xs2 [Yt] that have been stored in the memoryarrays. Further, the distance L between the ends is found by using theequation: (X1-Xs1 [Y])+Xs2 [Yt] (S187). First, it is set that XX=Xs1 [Y](S188), the density of the coordinates (XX, Y) on the first image memory105a found by using the equation: (D/L)(XX-Xs1 [Y])+DN1 [Y] (S189).

Thereafter, while shifting is made line by line with respect to theX-coordinate using the equation XX=XX+1 (S190), the steps S189 and S190are repeated until XX exceeds X1, that is, until it has been determinedthat XX <X1 is positive at S191. With this operation, the densities fromXs1 [Y] to X1 (the loss of data caused by the shadow- erasing operation)are estimated in a linear manner with respect to line Y of the firstimage memory 105a, and the compensation for loss of data is thus carriedout in accordance with the estimated densities.

Next, in order to make a compensation with respect to line Yt in thesecond image memory 105b, it is set that XX =0 (S192), the density ofthe coordinates (XX, Yt) on the second image memory 105b is found byusing the equation: (D/L)XX+DN1 [Y] (S193). Thereafter, while shiftingis made line by line with respect to XX (S194), the steps S193 and S194are repeated until XX exceeds Xs2 [Yt], that is, until it has beendetermined that XX>Xs2 [Yt] is positive at S194. With this operation,the densities from 0 to Xs2 [Yt] of XX are estimated in a linear mannerwith respect to line Yt of the second image memory 105b, and thecompensation for loss of data is thus carried out in accordance with theestimated densities.

Thereafter, while shifting is made line by line with respect to theY-coordinate using the equation Y=Y+1 (S196), the steps S182 throughS196 are repeated until the Y-coordinate exceeds Y2, that is, until ithas been determined that Y>Y2 is positive at S197. Thus, the densitiesin the XX-coordinate corresponding to the area that has been subject tothe shadow-erasing operation are estimated in a linear manner withrespect to line Y (or Yt) of the first and second image memories 105aand 105b, and the compensation for loss of data is carried out inaccordance with the estimated densities. When it is determined that Y>Y2is positive at S197, the compensating operation for the loss of data iscompleted.

Even if there are differences in the colors and densities of thecorresponding portions of images located on left and right pages asshown, for example, in FIG. 50, both of the pages can be joined to eachother smoothly by determining the densities of the data-loss areasthrough the above-mentioned compensating operation for the loss of data.

As described above, upon copying a book or the like having aconsiderable thickness, even if shadows are formed in the document datastored in the image memory due to the separation of the bound portion ofthe book from the document platen, the digital copying machine of thepresent embodiment carries out the compensating operation through thefollowing steps of: executing the shadow-erasing operation byrecognizing the ranges of the shadows accurately; calculating theamounts of positioning on the document data stored in the separatememories in accordance with the density distributions of the respectiveends of the images; estimating the densities of the data-loss area ofthe image caused by the shadow erasing operation in accordance with thecolors and densities of the corresponding ends of the images; andexecuting the compensation for the loss of data in accordance with theestimated densities so that no unnatural appearance occurs on thejointed portion. Further, as with the digital copying machine describedin the aforementioned embodiments, the variable magnification operationis automatically carried out in response to a specified size of copysheets, and the joined image can be formed on desired copy sheets orother materials.

Therefore, even in the case of using a document such as a book or thelike having a considerable thickness, the joining operation can becarried out accurately, and since troublesome and time consuming jobs,such as trimming and sticking together copy sheets copied separately toform one sheet of document, are no longer required, the efficiency ofwork can be improved. Further, since it is no longer necessary to makeunnecessary copies for use in trimming and sticking together to obtainone sheet of document, wasteful use of toner and copy sheets can beprevented. Moreover, shadows caused by the separation of the documentfrom the document platen can be completely erased, and the disadvantagethat necessary images are erased due to the shadow-erasing operation canbe avoided. Therefore, it is possible to ensure high-quality in thecopied images.

Referring to FIG. 2 as well as FIGS. 51 through 54, the followingdescription will discuss another embodiment of the present invention.Here, for convenience of explanation, those members that have the samefunctions and that are described in embodiment 1 are indicated by thesame reference numerals and the description thereof is omitted.

Further, as with the digital copying machine described in theaforementioned embodiments, a digital copying machine of the presentembodiment has a structure shown in FIG. 2, and an image processingsection, which is installed in the digital copying machine, has aconstruction as shown in FIG. 51.

The following description will discuss the construction, functions, etc.of the image processing section for suitably processing the image dataand for releasing the data to the laser driver unit 7.

As shown in FIG. 51, the image processing section is constituted of aRGB level-adjusting section 40, an A/D conversion section 41, a shadingcorrection section 42, an image memory 43, a division-enlargementprocessing section 121, a τ correction section 49, a masking section 51,a UCR(Under Color Removal)-BP(Black Print) processing section 52, asharpness filter 53, a variable magnification section 54, a densityprocessing section 55, a color-balance adjusting section 56, and toneprocessing section 57.

After having been subject to the corresponding processing in the RGBlevel-adjusting section 40, the A/D conversion section 41, and theshading correction section 42, image data of R, G, B obtained from theCCD sensor 6 are temporarily stored in the image memory 43 as describedearlier. The image memory 43 has a storage capacity equivalent to atleast two document pages of image data, and data of the next documentare stored in the same manner.

Here, if the division-enlargement mode has been specified, the imagedata stored in the image memory 43 are sent to the division-enlargementprocessing section 121. In the division-enlargement processing section121, two types of processing are carried out: processing for dividingthe image data of the document and corrective processing for allowingends of the divided image data to be smoothly connected to other ends ofthe divided image data.

The division-enlargement processing section 121 is provided with adivision-number/border decision section 122, a division-magnificationprocessing section 123, an image positioning section 124, ajoint-portion correction section 125, and a margin-portion creatingsection 126.

The division-number/border decision section 122 recognizes the positionof the document and the ends of the document, thereby recognizing thesize of the image data. Then, taking account of the size of the imagedata and an enlargement ratio or a size of copy sheet that has beenspecified, the decision-number/border decision section 122 calculatesthe size of copy sheet or the enlargement ratio that is required, andjudges whether or not the corresponding size of copy sheet or thecorresponding enlargement ratio is available. In other words, it decideswhether or not the division processing is possible. If the divisionprocessing is possible, it decides the number of divided image data,that is, the number of copy sheets that are required to copy the dividedimage data, and also decides borders by which the image data aredivided.

In the division-magnification processing section 123, the image data aredivided according to the number of division and the borders that aredetermined in the division-number/border decision section 122, and amagnification processing is carried out on each divided image. Then,each of the divided images is formed into a separated image to be copiedon one copy sheet. Further, if necessary, conversion of the coordinatesis carried out so that the lengthwise direction of the image coincideswith the lengthwise direction of the copy sheet.

In the image positioning section 124, data corresponding to necessary,predetermined lines are read from each border of the divided images,that is, each portion forming a joint between the divided images, andpositioning is carried out by arranging the image data of the documentso that edges having consistent data are joined. Then, the consistencyof the data is confirmed, and, if necessary, the best-suited position ofthe image data is found by shifting the positions of the image data.These operations are executed in order to prevent occurrences of visibledifferences along the borders of the divided images. More specifically,the resolution is lowered due to the enlargement processing in thedivision-magnification processing section 123, and this causes fewerimage data per area; therefore, it is quite possible that visibledifferences appear along the borders of the divided images that arereleased from the present copying machine. To counteract this, theconsistency of the images between the joint portions is confirmed in theimage positioning section 124.

In the joint-portion correction section 125, corrections such ascompensation for lack of data and elimination of excess data between thejoint portions are carried out so that the consistency of the databetween the joint portions is suitably maintained.

In the margin-portion creating section 126, a margin portion is formedalong one of the joint portions of the images that are to be joined. Themargin portion is determined by adding data that impart a color theretowhen it is copied on a copy sheet. The image data thus treated in themargin-portion creating section 126 are again stored in the image memory43.

As shown in FIG. 53, assuming that the superimposed portion of C, M, Yis min (C, M, Y) in given data, the following equations hold in therelationship between the amounts of respective toners C, M, Y before theprocessing and the amounts of respective toners C', M', Y' and theamount of black toner B_(K) after the processing.

    B.sub.K =α.min(C.M.Y)

    C'=C-β.min(C.M.Y)

    M'=M-β.min(C.M.Y)

    Y'=Y-β.min(C.M.Y)

where α represents ink rate (0≦α≦1) and β represents UCR (%).

Referring to the flow chart of FIG. 52, an explanation will be given onthe operation of the copying machine of the present embodiment whereinthe division-enlargement mode is specified.

For example, in the case of executing a division-enlargement processingon a document shown in FIG. 54(a), a division-enlargement mode isspecified through an operation on an operation panel, not shown, withthe document placed on the document platen 27 (S201), and theenlargement ratio of the document or the size of copy sheet whereon thedocument is copied in a divided manner is specified (S202).

After the above specifying operations, a scanning is conducted on thedocument by the scanner unit 22 (S203). Then, the image data obtainedfrom the CCD sensor 6 through the scanning are subject to theaforementioned various types of processing through the RGBlevel-adjusting section 40, the A/D conversion section 41 and theshading correction section 42 (S204), and the subsequent image data arestored in the image memory 43 (S205).

Next, the division-number/border decision section 122 in thedivision-enlargement processing section 121 recognizes the position ofthe document and the ends of the document (S206). Thus, the size of theimage data is recognized, and the size or the enlargement ratio of anecessary copy sheet is calculated based on the size of the image dataand the enlargement ratio or the size of copy sheet that has beenspecified at S202, and then judgement is made as to whether or not thecorresponding size or enlargement ratio of copy paper is available. Inother words, judgement is made as to whether or not thedivision-enlargement processing is possible by determining whether ornot the necessary copy sheets are provided to be fed or whether or notthe necessary enlargement ratio is selectable in the copying machine(S207). If the judgement is made as "NO" at S207, a warning display isgiven on the display section of the operation panel (S216), therebycompleting the operation.

Conversely, if the judgement is made as "YES" at S207, the number ofdivided image data, that is, the number of copy sheets that are requiredto copy the divided image data, is determined, and borders by which theimage data are divided are determined (S208).

Next, in the division magnification processing section 123, the image isdivided according to the borders that have been determined at S208(S209), and a magnification processing is conducted on each dividedimage (S210). Each of the divided images is formed into a separatedimage to be copied on one copy sheet. Further, if necessary, conversionof the coordinates is carried out so that the lengthwise direction ofthe image coincides with the lengthwise direction of the copy sheet.

In the image positioning section 124, data corresponding to several tensof lines from each border of the divided images forming a joint betweenthe divided images, that is, data located within a retrieving area Pshown in FIG. 54(b), are read, and positioning is carried out byarranging the respective image data so that edges having consistent dataare joined, and then the consistency of the data is confirmed (S211).

During this operation, if necessary, the best-suited position of theimage data is found by checking the consistency of the data whileshifting the image data of one side in the main scanning direction or inthe sub scanning direction with the image data of the other sidemaintained in a fixed state. Further, the judgement on the consistencyof the image data is made, for example, as follows: First, features ofrespective image data are extracted by recognizing peculiar lines orcharacters included in the image data or by recognizing the arrays,features of patterns, colors, etc. of the data, and the features thusextracted are digitized and stored. Then, these features are comparedwith one another to make the judgement.

Next, in the joint-portion correction section 125, corrections such ascompensation for lack of data and elimination of excess data between thejoint portions are carried out so that the joint portions of therespective images are smoothly joined to each other (S212). In thisoperation, the edges of corresponding joint portions are connected tohypothetical lines, and by recognizing the connected lines and the edgesof the respective images, the whole image are connected by smoothstraight lines.

In the margin-portion creating section 126, a margin portion Q is formedalong one of the Joint portions of the images that are to be joined asillustrated in FIG. 54(b) (S213). The margin portion is determined byadding data that impart a color thereto when it is copied on a copysheet.

After completion of the processing in the division-enlargementprocessing section 121, respective image data are separately stored inthe image memory 43 as independent image data.

Thereafter, the aforementioned various types processing are conducted onthe respective image data through the τ-correction section 49, themasking section 51, the UCR-BP processing section 52, the sharpnessfilter 53, the variable magnification section 54, the density processingsection 55, the color-balance adjusting section 56 and the toneprocessing section 57 (S214), and the subsequent image data are copiedon separated copy sheets respectively (S215).

With this arrangement in the present embodiment, an image shown in FIG.54(a) is divided into, for example, four portions as is shown in FIG.54(b), and copied onto individual copy sheets. Further, a colored marginportion Q is formed along one of the joint portions of the copied imagesthat are to be joined. By applying paste, etc. to the margin portions Q,the copied images are joined to one another to form one complete copiedimage that is enlarged to a great degree, and this joining work iseasily conducted.

Additionally, in the present embodiment the margin portions are coloredso that they are clearly distinguished; yet, any treatment may beadopted instead of the above arrangement as long as it clearlyidentifies the margin portions. For example, those treatments include:dividing the margin portions from the images by lines with low density;and applying slanting lines with low density to the margin portions.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

What is claimed is:
 1. An image processing apparatus comprising:input means for reading an image from one sheet of an original document; storage means for storing the image of one sheet read by the input means as image data; division-number/border decision section for determining the operability of a dividing process based on size of the image data stored in the storage means and at least one of a specified magnification rate and a size of available recording media, and for determining a number of divisions and borders of image divisions appropriate for dividing the image upon determining that the dividing process is operable; division-enlargement means, upon the division-number/border decision section determining that the dividing process is operable, for dividing the image data stored in the storage means into a plurality of partial image data based upon the determined number of divisions and borders, and for enlarging the plurality of partial image data; copying means for copying each of a plurality of the enlarged image data onto a separate sheet of recording medium; a margin-portion creating section which, for at least one of the plurality of enlarged partial image data prior to supply to the copying means, adds a joint portion to one of a pair of adjacent partial image data to create a pasting margin by which adjacent copied images, on separate sheets of recording media thereafter produced by the copying means, can be joined together.
 2. The image processing apparatus as defined in claim 1, wherein the margin-portion creating section provides color data to color the added joint portion.
 3. A method for enlarging and recording image data on a plurality of recording media in a divided manner, comprising the steps of:specifying at least one of a scale of enlargement of an original document, and a size of recording media for recording images; reading the original document of a single sheet and storing an image thereof as image data; recognizing a size of the stored image data and determining the operability of dividing and enlarging processes based on the recognized size and the specified at least one of the scale of enlargement and size of recording media; determining a number of divisions and borders of image divisions appropriate for dividing the image, upon determining that the dividing and enlarging processes are operable; dividing the stored image data into a plurality of partial image data based upon the determined number of divisions and borders and enlarging the respective partial image data; copying each of a plurality of the enlarged image data onto a separate sheet of recording medium; and adding a joint portion to one of a pair of adjacent partial image data prior to copying, to create a pasting margin by which adjacent copied images on separate sheets of recording media, can be joined together.
 4. The method of claim 3, further comprising the step of:coloring the added joint portion with color data. 